All practice questions

5556 questions

Question 1601Question

Let xx, yy, and zz be integers such that x<y<z|x| < |y| < |z|, x+y+z=3x + y + z = -3, and xyz>0xyz > 0. What is the smallest possible value of xy+yz+zx|x - y| + |y - z| + |z - x|?

Show answer & explanation

Answer: 12

Answer

12
The correct answer is 12. To satisfy the given conditions, the product xyz>0xyz > 0 means either all three numbers are positive, or exactly two are negative. Since they sum to 3-3, they cannot all be positive. Letting two be negative and one positive, we find that the integer set {1,2,4}\{-1, 2, -4\} satisfies 1<2<4|-1| < |2| < |-4| (or 1<2<41 < 2 < 4), has a sum of 3-3, and a product of 8>08 > 0. The sum of the absolute differences is 12+2(4)+4(1)=3+6+3=12|-1 - 2| + |2 - (-4)| + |-4 - (-1)| = 3 + 6 + 3 = 12, which is the minimum possible value.

Step-by-Step Solution

1
Analyze the sign constraints from the product condition xyz>0xyz > 0.
Since the product of xx, yy, and zz is positive, either all three integers are positive, or exactly two are negative and one is positive.
The product of three numbers is positive if there are zero or two negative factors.
2
Evaluate the case where all three integers are positive.
If all three are positive, then x,y,z1x, y, z \geq 1. This implies their sum x+y+z3x+y+z \geq 3, which contradicts the constraint x+y+z=3x+y+z = -3. Thus, this case is impossible.
Positive integers cannot sum to a negative number.
3
Analyze the case where two integers are negative and one is positive, and express them in terms of their absolute values.
Let the negative integers be u-u and v-v (with u>v>0u > v > 0) and the positive integer be p>0p > 0. The sum constraint becomes uv+p=3-u - v + p = -3, which simplifies to p=u+v3p = u + v - 3. The absolute values are uu, vv, and pp, which must be three distinct positive integers satisfying x<y<z|x| < |y| < |z|.
This translates the constraints into positive integer variables representing the absolute values.
4
Determine the values of u,v,pu, v, p that minimize the maximum difference between any two of the three integers x,y,zx, y, z.
For v=1v = 1: if u=4u = 4, then p=2p = 2. The absolute values {1,2,4}\{1, 2, 4\} are distinct. The corresponding integers are x=1x = -1, y=2y = 2, and z=4z = -4. Their sum is 3-3 and product is 8>08 > 0. The difference between the maximum and minimum values is 2(4)=62 - (-4) = 6. For v=2v = 2: if u=4u = 4, then p=3p = 3. The absolute values {2,3,4}\{2, 3, 4\} are distinct, giving the integers 4,2,3-4, -2, 3, with a maximum difference of 3(4)=73 - (-4) = 7. For higher values, the difference only increases.
The expression xy+yz+zx|x - y| + |y - z| + |z - x| is equal to twice the difference between the maximum and minimum of the three integers.
5
Calculate the minimum value of the expression.
Using the optimal set x=1,y=2,z=4x = -1, y = 2, z = -4, the value of the expression is 12+2(4)+4(1)=3+6+3=12|-1 - 2| + |2 - (-4)| + |-4 - (-1)| = 3 + 6 + 3 = 12.
This is the smallest possible sum of the absolute differences.

Key Concept

Using absolute values and sign analysis to solve system of constraints on integers and distances on a number line.
Question 1602Question

A positive integer is said to have exactly 88 positive factors. What is the fifth smallest positive integer that satisfies this condition?

Show answer & explanation

Answer: 54

Answer

The fifth smallest positive integer with exactly 8 positive factors is 54.
The fifth smallest positive integer with exactly 8 positive factors is 54. The number of factors of n=p1a1pkakn = p_1^{a_1} \cdots p_k^{a_k} is (a1+1)(ak+1)=8(a_1+1)\cdots(a_k+1) = 8. The possible factorization shapes are p7p^7 (smallest is 128), p3qp^3 q (smallest are 24, 40, 54, 56, 88), and pqrp q r (smallest are 30, 42, 66, 70). Sorting these gives 24, 30, 40, 42, 54, 56, 66, 70, 78, 88, where 54 is the fifth value.

Step-by-Step Solution

1
Relate the number of positive factors to the prime factorization of a positive integer.
The number of positive factors is (a1+1)(a2+1)(ak+1)=8(a_1 + 1)(a_2 + 1) \cdots (a_k + 1) = 8.
This formula counts all possible combinations of prime factors that form divisors.
2
Determine the possible prime factorization structures that yield exactly 8 factors.
The possible prime factor structures are p7p^7, p3qp^3 q, and pqrp q r for distinct primes pp, qq, and rr.
These correspond to the integer factorizations of 8: 8, 4×24 \times 2, and 2×2×22 \times 2 \times 2.
3
List the smallest candidate values for each structure.
Candidates include 128 (for p7p^7); 24, 40, 54, 56, 88 (for p3qp^3 q); and 30, 42, 66, 70 (for pqrp q r).
Evaluating structures with the smallest available prime numbers (2, 3, 5, 7, etc.) yields the smallest positive integers.
4
Sort all the candidates in ascending order.
The sorted list of smallest values is 24, 30, 40, 42, 54, 56, 66, 70, 78, 88.
Sorting allows us to identify the fifth smallest value precisely.
5
Identify the fifth value in the sorted list.
The fifth element is 54.
Counting from the smallest value (24) to the fifth position yields 54.

Key Concept

Determining the number of factors of an integer from its prime factorization.
Question 1603Question

What integer represents the midpoint between 9-9 and 77 on a standard number line?

Show answer & explanation

Answer: 1-1

Answer

The midpoint coordinate is 1-1.
The midpoint of two numbers on a number line is their mathematical average. Adding the coordinates 9-9 and 77 gives a sum of 2-2. Dividing this sum by 22 yields the midpoint coordinate of 1-1.

Step-by-Step Solution

1
Identify the coordinates of the two endpoints on the number line.
The endpoints are 9-9 and 77.
Before calculating the midpoint, we must identify the values of the two points given in the problem.
2
Find the average of the two coordinates using the midpoint formula a+b2\frac{a + b}{2}.
9+72=22=1\frac{-9 + 7}{2} = \frac{-2}{2} = -1.
The midpoint of any two coordinates on a number line is their arithmetic mean.

Key Concept

Finding the midpoint between two integers on a number line
Estimated Time:45s
Question 1604Question

What is the value of the mathematical expression below?

18÷3×2(68)3-18 \div 3 \times 2 - (6 - 8)^3
Show answer & explanation

Answer: -4

Answer

-4
Evaluating the expression according to the order of operations (PEMDAS) yields the correct value. First, simplify the expression within the parentheses to get 68=26 - 8 = -2. Second, evaluate the exponent to get (2)3=8(-2)^3 = -8. Next, perform multiplication and division from left to right: first divide 18-18 by 33 to get 6-6, then multiply by 22 to get 12-12. Finally, perform the subtraction: 12(8)=12+8=4-12 - (-8) = -12 + 8 = -4.

Step-by-Step Solution

1
Evaluate the expression inside the parentheses.
6 - 8 = -2
According to the order of operations (PEMDAS), operations inside parentheses must be evaluated first.
2
Evaluate the exponent.
(-2)^3 = -8
Exponents are evaluated next. A negative number raised to an odd power yields a negative result.
3
Perform the division.
18÷3=6-18 \div 3 = -6
Multiplication and division have equal priority and must be performed from left to right.
4
Perform the multiplication.
6×2=12-6 \times 2 = -12
Continuing from left to right, perform the multiplication next.
5
Perform the subtraction.
-12 - (-8) = -12 + 8 = -4
Finally, perform the subtraction. Subtracting a negative number is equivalent to adding its positive counterpart.

Key Concept

Order of Operations (PEMDAS) with negative numbers and exponents
Estimated Time:1m 0s
Question 1605Question

On a map of a city, the scale is 0.5 inches=12 miles0.5\text{ inches} = 12\text{ miles}. If the actual distance between two towns is 96 miles96\text{ miles}, what is the distance between the two towns on the map, in inches?

Show answer & explanation

Answer: 4

Answer

4 inches
To find the distance on the map, we set up the proportion comparing map inches to actual miles: 0.5 inches12 miles=x inches96 miles\frac{0.5\text{ inches}}{12\text{ miles}} = \frac{x\text{ inches}}{96\text{ miles}}. Cross-multiplying gives 12x=4812x = 48, which simplifies to x=4x = 4. Therefore, the distance on the map is 4 inches4\text{ inches}.

Step-by-Step Solution

1
Set up a proportion to relate the map distance to the actual distance.
0.5 inches12 miles=x inches96 miles\frac{0.5\text{ inches}}{12\text{ miles}} = \frac{x\text{ inches}}{96\text{ miles}} where xx represents the distance between the two towns on the map.
This establishes a direct proportion based on the map's scale.
2
Solve for the unknown variable xx by cross-multiplying.
12x=0.59612 \cdot x = 0.5 \cdot 96
12x=4812x = 48
Cross-multiplication is the standard algebraic method to solve proportions.
3
Divide both sides of the equation by 12 to find xx.
x=4812=4x = \frac{48}{12} = 4
Isolating the variable gives the final map distance.

Key Concept

Solving ratio scale problems by setting up and solving proportions.
Question 1606Question

Let xx and yy be integers such that x4|x| \leq 4 and y4|y| \leq 4. How many distinct pairs of integers (x,y)(x, y) satisfy the inequality xy2||x| - |y|| \geq 2?

Show answer & explanation

Answer: 36

Answer

There are 36 distinct pairs of integers (x,y)(x, y) that satisfy the inequality.
By analyzing the possible values for x|x| and y|y| within the set {0,1,2,3,4}\{0, 1, 2, 3, 4\}, we identify the 12 pairs that satisfy the inequality xy2||x| - |y|| \geq 2. When mapping these absolute values back to the actual integer coordinates, we account for the single option when a coordinate is 0 and the two positive/negative options when a coordinate is non-zero. Summing these possibilities yields exactly 36 distinct pairs.

Step-by-Step Solution

1
Determine the range of absolute values for the integers.
The possible values for x|x| and y|y| are {0,1,2,3,4}\{0, 1, 2, 3, 4\}.
Since xx and yy are integers satisfying 4x,y4-4 \leq x, y \leq 4, their absolute values must be non-negative integers up to 4.
2
Find the pairs of absolute values (x,y)(|x|, |y|) that satisfy the inequality.
The valid pairs are: (0,2),(0,3),(0,4),(1,3),(1,4),(2,0),(2,4),(3,0),(3,1),(4,0),(4,1),(4,2)(0, 2), (0, 3), (0, 4), (1, 3), (1, 4), (2, 0), (2, 4), (3, 0), (3, 1), (4, 0), (4, 1), (4, 2).
We test all combinations of u,v{0,1,2,3,4}u, v \in \{0, 1, 2, 3, 4\} such that uv2|u - v| \geq 2.
3
Calculate the number of integer coordinate pairs (x,y)(x, y) corresponding to each absolute value pair.
Pairs with one zero value yield 2 integer solutions (e.g., u=0,v=2(0,2),(0,2)u=0, v=2 \Rightarrow (0, 2), (0, -2)). Pairs with both non-zero values yield 4 integer solutions (e.g., u=1,v=3(1,3),(1,3),(1,3),(1,3)u=1, v=3 \Rightarrow (1, 3), (1, -3), (-1, 3), (-1, -3)).
An absolute value of 0 corresponds to only 1 integer (00), whereas any positive absolute value kk corresponds to 2 integers (kk and k-k).
4
Sum the number of integer pairs for all valid cases.
Total pairs = (3×2)+(3×2)+(6×4)=6+6+24=36(3 \times 2) + (3 \times 2) + (6 \times 4) = 6 + 6 + 24 = 36.
There are 3 pairs with u=0u=0 (66 solutions), 3 pairs with v=0v=0 (66 solutions), and 6 pairs with both u,v>0u, v > 0 (2424 solutions).

Key Concept

Solving nested absolute value inequalities with integer constraints and counting solution pairs systematically.
Question 1607Question

The writer wants to add the following sentence to the paragraph:

'These disparate sheets were often stored loosely in scrolls or portfolios, which made them prone to damage and difficult to consult.'

[1] In 1570, Flemish cartographer Abraham Ortelius published the *Theatrum Orbis Terrarum*, which is widely considered the first modern atlas. [2] Prior to this publication, maps were printed in various sizes and formats, making them difficult to bind or compare. [3] Ortelius resolved this issue by compiling existing maps, engraving them onto uniform copper plates, and printing them as a cohesive book. [4] This standardized format revolutionized cartography, allowing merchants and scholars to view the entire known world in a single, organized volume.

To make the paragraph most logical, where should this sentence be placed?

Show answer & explanation

Answer: after Sentence 2

Answer

after Sentence 2
The correct answer is the option that places the sentence after Sentence 2. Sentence 2 introduces 'maps... printed in various sizes and formats', which provides the necessary antecedent for the pronoun phrase 'These disparate sheets' at the beginning of the target sentence. Additionally, the target sentence describes the storage and consultation difficulties of those maps, setting up the transition to Sentence 3, where Abraham Ortelius resolves 'this issue' by printing uniform maps in a single book.

Step-by-Step Solution

1
Identify logical and grammatical clues in the target sentence.
The target sentence begins with the phrase 'These disparate sheets' and describes a problem (loose storage, damage, difficulty in consulting maps).
Recognizing the pronoun antecedent ('These disparate sheets') and the context (a problem description) helps locate where the sentence belongs relative to other sentences.
2
Locate the logical antecedent for the pronoun phrase in the paragraph.
Sentence 2 mentions 'maps... printed in various sizes and formats'. These are the 'disparate sheets' referred to in the target sentence.
A sentence containing a specific pronoun reference must follow the sentence that introduces the noun it references.
3
Evaluate the flow of the entire paragraph with the sentence inserted.
If placed after Sentence 2, the paragraph describes the pre-atlas situation (Sentence 2), details the storage problems of that situation (target sentence), and then introduces Ortelius's solution to 'this issue' (Sentence 3).
Ensuring the narrative progression makes sense chronologically and conceptually confirms the correct placement.

Key Concept

Identifying pronoun references and logical transitions to determine sentence placement.
Estimated Time:1m 0s
Question 1608Question

[1] During a chilly trolley ride in New York City in 1902, Mary Anderson noticed that the motorman had to open the front window to wipe away the accumulating sleet. [2] This forced the driver to endure the freezing wind and rain just to maintain a clear view of the street ahead. [3] Upon returning home to Alabama, she sketched a design for a rubber blade that could be operated from inside the vehicle by turning a hand lever. [4] Many manufacturing firms initially refused to purchase the rights to the design, dismissing it as a dangerous distraction to drivers. [5] This manual wiper, which she patented the following year, successfully kept the window clean without requiring the driver to open the glass.

To make this paragraph most logical and cohesive, where should Sentence 5 be placed?

Show answer & explanation

Answer: after Sentence 3

Answer

after Sentence 3
Placing the sentence after Sentence 3 is correct because the demonstrative phrase 'This manual wiper' in the sentence to be placed directly references the 'rubber blade' and 'hand lever' introduced in Sentence 3. This placement also preserves the chronological timeline: she sketched the design first, patented it next, and then manufacturing firms rejected the rights to that design.

Step-by-Step Solution

1
Analyze Sentence 5 for pronoun referents and logical markers.
Sentence 5 begins with 'This manual wiper,' indicating it must follow a sentence that introduces a wiper or blade mechanism.
Identifying pronoun antecedents establishes logical links between sentences.
2
Trace the chronological development of the invention within the paragraph.
Sentence 3 describes sketching the design, Sentence 5 describes patenting it the following year, and Sentence 4 describes firms refusing to purchase the rights to that design.
Historical narrative paragraphs must follow a chronological sequence of events to make sense.
3
Verify the placement of Sentence 5 after Sentence 3.
The flow is established: designing the device (Sentence 3) -> describing how the patented device worked (Sentence 5) -> discussing the commercial rejection of the design (Sentence 4).
This ordering keeps the noun phrase and pronoun referent together while maintaining proper chronological and cause-and-effect transitions.

Key Concept

Sentence Reordering and Placement
Estimated Time:1m 15s
Question 1609Question

A high-speed fiber-optic cable transmits data at a rate of 8.0×1078.0 \times 10^7 bytes per second. A digital archive containing a total of 3.2×10113.2 \times 10^{11} bytes needs to be transmitted. How many seconds will it take to complete the transmission?

Show answer & explanation

Answer: 4.0×1034.0 \times 10^3

Answer

The transmission will take 4.0×1034.0 \times 10^3 seconds.
The correct answer represents the transmission time of 4.0×1034.0 \times 10^3 seconds. This is determined by dividing the total data volume, 3.2×10113.2 \times 10^{11} bytes, by the rate, 8.0×1078.0 \times 10^7 bytes per second. The division yields 3.28.0×10117=0.4×104\frac{3.2}{8.0} \times 10^{11 - 7} = 0.4 \times 10^4. Converting this value to standard scientific notation by moving the decimal point one digit to the right reduces the power of 1010 by one, resulting in 4.0×1034.0 \times 10^3.

Step-by-Step Solution

1
Set up the division to find the transmission time.
Time=3.2×1011 bytes8.0×107 bytes/second\text{Time} = \frac{3.2 \times 10^{11}\text{ bytes}}{8.0 \times 10^7\text{ bytes/second}}
To find the total time, divide the total quantity of data by the transmission rate.
2
Divide the numerical coefficients.
3.28.0=0.4\frac{3.2}{8.0} = 0.4
When dividing numbers written in scientific notation, divide the coefficients first.
3
Apply the quotient rule of exponents to the powers of 10.
1011107=10117=104\frac{10^{11}}{10^7} = 10^{11 - 7} = 10^4
Subtract the exponent in the denominator from the exponent in the numerator.
4
Combine the intermediate parts and convert to standard scientific notation.
0.4×104=4.0×1030.4 \times 10^4 = 4.0 \times 10^3
Standard scientific notation requires the coefficient to be at least 1 but strictly less than 10. Shifting the decimal point one place to the right decreases the exponent by 1.

Key Concept

Dividing numbers in scientific notation and converting to standard form
Estimated Time:1m 0s
Question 1610Question

Read the following passage segment:

Although the new commercial drone is capable to fly in turbulent weather, the operators decided to postpone the survey flight until the storm subsided.

Which of the following options represents the correct idiomatic phrasing for the underlined portion of the sentence?

Show answer & explanation

Answer: capable of flying

Answer

capable of flying
The correct answer is 'capable of flying' because standard English usage dictates that the adjective 'capable' must be paired with the preposition 'of' followed by a gerund (a verb ending in -ing acting as a noun). Therefore, the construction 'capable of flying' is the only idiomatically correct choice.

Step-by-Step Solution

1
Identify the underlined phrase and the word that dictates the idiom.
The word is the adjective 'capable'.
Understanding which word governs the prepositional phrase is key to finding the correct idiomatic pairing.
2
Determine the standard idiomatic construction for 'capable'.
The adjective 'capable' must be paired with 'of' followed by a gerund ('capable of doing something').
Using any other preposition or the infinitive form (such as 'to fly') violates standard English idiomatic usage.
3
Evaluate the choices to find the one that fits this construction.
The phrase 'capable of flying' correctly uses the preposition 'of' and the gerund 'flying'.
This matches the required idiomatic pattern.

Key Concept

The adjective 'capable' must be followed by the preposition 'of' and a gerund (verb + -ing) to be idiomatically correct.
Estimated Time:1m 0s
Question 1611Question

A cleaning mixture is prepared by combining bleach and water in a ratio of 1:81:8. If a container holds a total of 3636 cups of this mixture, how many cups of bleach were used?

Show answer & explanation

Answer: 44

Answer

4 cups
The correct answer is 4. The ratio of bleach to water is 1:81:8, which means the entire mixture is divided into 1+8=91 + 8 = 9 equal parts. Bleach constitutes 19\frac{1}{9} of the overall mixture. By taking 19\frac{1}{9} of the 3636-cup total volume, we find that the amount of bleach used is 44 cups.

Step-by-Step Solution

1
Determine the total parts in the mixture's ratio.
1+8=91 + 8 = 9 total parts
Since the ratio of bleach to water is 1:81:8, the mixture is composed of 11 part bleach for every 88 parts water.
2
Express the bleach portion as a fraction of the total mixture.
19\frac{1}{9}
The bleach represents 11 part out of the 99 total parts in the mixture.
3
Find the amount of bleach in the 3636-cup container.
19×36=4\frac{1}{9} \times 36 = 4 cups
Multiply the fraction of bleach by the total volume of the cleaning mixture.

Key Concept

Determining a part from a part-to-part ratio and a total quantity
Question 1612Question

Passage Excerpt:

In the early nineteenth century, a Cherokee silversmith named Sequoyah became convinced that written language was the key to his people's independence. Over the course of a decade, he painstakingly designed a system of eighty-five characters representing the syllables of the spoken Cherokee language. His invention allowed Cherokee speakers to achieve literacy rapidly, leading to the establishment of the first Native American newspaper, *The Cherokee Phoenix*, in 1828.

Given that all the choices are grammatically correct, which choice most clearly and vividly emphasizes the widespread and immediate adoption of Sequoyah's system by the Cherokee community?

Show answer & explanation

Answer: Within months, thousands of Cherokee people learned to read and write the new script

Answer

The option stating that within months, thousands of Cherokee people learned to read and write the new script is the correct choice.
The correct option provides specific, vivid details that show both immediate ('Within months') and widespread ('thousands of Cherokee people') adoption of the script, fulfilling the rhetorical goal outlined in the prompt.

Step-by-Step Solution

1
Analyze the prompt to identify the specific rhetorical constraints required.
The prompt requires details showing both 'widespread' (large scale) and 'immediate' (fast or sudden) adoption of the writing system.
This establishes the criteria against which all options must be measured.
2
Evaluate the choices to check which ones fulfill both parts of the rhetorical goal.
The option highlighting 'Within months' (immediate) and 'thousands of Cherokee people' (widespread) satisfies both criteria. The other options either discuss long-term uses, detail the creator's struggles, or contain grammatical errors.
This narrows down the candidates to the rhetorically appropriate choice.
3
Check the remaining candidate for grammatical accuracy.
The correct option is grammatically sound, whereas the option containing 'they taught their neighbors' is a comma splice.
ACT English questions require the correct choice to be both rhetorically and grammatically correct.

Key Concept

Meeting Specific Rhetorical Goals
Estimated Time:1m 0s
Question 1613Question

An artist has a rectangular sheet of stained glass that measures 8484 inches by 120120 inches. The artist wants to cut the sheet into congruent square tiles of the largest possible side length, such that there is no glass wasted. What is the total number of square tiles the artist will obtain?

Show answer & explanation

Answer: 70

Answer

The total number of square tiles the artist will obtain is 70.
To find the maximum side length of the square tiles without wasting any glass, we must find the greatest common factor (GCF) of the rectangular dimensions, 8484 and 120120. The prime factorizations are 84=22×3×784 = 2^2 \times 3 \times 7 and 120=23×3×5120 = 2^3 \times 3 \times 5, which gives a GCF of 22×3=122^2 \times 3 = 12 inches. The number of square tiles that fit along the length is 84÷12=784 \div 12 = 7 and along the width is 120÷12=10120 \div 12 = 10. Multiplying these dimensions gives a total of 7×10=707 \times 10 = 70 square tiles.

Step-by-Step Solution

1
Determine the prime factorizations of the dimensions of the sheet.
84=22×3×784 = 2^2 \times 3 \times 7 and 120=23×3×5120 = 2^3 \times 3 \times 5
This allows finding the greatest common factor of the two side lengths.
2
Calculate the greatest common factor (GCF) of 8484 and 120120.
GCF(84,120)=22×3=12\text{GCF}(84, 120) = 2^2 \times 3 = 12
The largest congruent squares that can tile the sheet without waste must have a side length equal to this GCF.
3
Divide each dimension of the sheet by the tile side length to find the number of tiles along each side.
84÷12=784 \div 12 = 7 tiles along the width, and 120÷12=10120 \div 12 = 10 tiles along the length.
This determines the grid dimensions of the tiles.
4
Multiply the number of tiles along the width by the number of tiles along the length.
7×10=707 \times 10 = 70
The total number of square tiles is the product of the number of tiles along each dimension.

Key Concept

Greatest Common Factor (GCF) application to division of a two-dimensional grid
Question 1614Question

In 1856, eighteen-year-old chemist William Henry Perkin was attempting to synthesize quinine, a treatment for malaria, in his home laboratory. Instead of obtaining the expected clear liquid, he produced a dark, sticky sludge. Rather than discarding the failed experiment, Perkin washed the flask with alcohol and noticed a beautiful purple residue. This accidental discovery resulted in mauveine, the world’s first synthetic organic dye. Before Perkin’s breakthrough, purple textiles were exceedingly rare, as the color could only be extracted from expensive natural sources like marine snails. Consequently, Perkin's new dye became super popular and hit it big in the nineteenth-century fashion industry, transforming the worlds of chemistry and apparel design.

Given that all the choices are grammatically correct, which one best maintains the established tone and style of the passage?

Show answer & explanation

Answer: achieved widespread commercial success

Answer

achieved widespread commercial success
The correct answer maintains the passage's neutral, historical, and academic tone. It is concise, direct, and matches the formal register established in the rest of the text.

Step-by-Step Solution

1
Analyze the context and tone of the passage.
The passage is a historical and scientific account of the discovery of mauveine, written in a neutral, informative, and academic tone.
Understanding the established style helps identify which choice matches the tone of the surrounding text.
2
Evaluate the underlined phrase and the choices for stylistic appropriateness.
The underlined phrase 'became super popular and hit it big' is highly colloquial and informal, which is inappropriate. The wordy option introduces redundant phrasing. The overly ornate option introduces pretentious terminology that distracts from the narrative. The correct option is concise, clear, and maintains the proper academic register.
Eliminating options that violate tone, conciseness, or register guidelines leads to the correct choice.

Key Concept

Stylistic Appropriateness
Estimated Time:1m 0s
Question 1615Question

In 1911, explorer Hiram Bingham climbed into the Peruvian Andes and encountered Machu Picchu, an ancient citadel from the past that was built by the Inca.

Which choice best replaces the underlined portion of the passage to eliminate redundancy?

Show answer & explanation

Answer: an ancient citadel built by the Inca

Answer

an ancient citadel built by the Inca
The correct choice is the most concise option that avoids redundancy. The modifier 'ancient' already expresses that the citadel is old and from the past, making the phrase 'from the past' redundant. The correct option expresses the idea directly and grammatically.

Step-by-Step Solution

1
Identify the redundancy in the underlined portion.
The words 'ancient' and 'from the past' express the same chronological concept.
To make the sentence clear and concise, repetitive synonyms must be eliminated.
2
Evaluate the remaining options for conciseness and grammatical correctness.
The most concise version is 'an ancient citadel built by the Inca', while the other choices introduce grammatical errors like comma splices or sentence fragments.
ACT conventions require both grammatical correctness and the elimination of redundant information.

Key Concept

Eliminating Redundancy
Question 1616Question

The passage below discusses the ecology of deep-sea hydrothermal vents. Read the passage and determine which precise and clear verb best completes the sentence to describe the ecological relationship between the primary-producing bacteria and the surrounding community. Which word best completes the blank?

Fill in the blanks below

Deep-sea hydrothermal vents support unique ecosystems that thrive in the complete absence of sunlight. Instead of relying on photosynthesis, the bacteria at the base of this food web utilize chemosynthesis to convert inorganic chemicals into energy. This biological process allows these microorganisms to a diverse community of tube worms, crabs, and other specialized organisms in one of the earth's most extreme environments.
Show answer & explanation

Answer

sustain (or a precise synonym such as 'support' or 'nourish')
The correct verb must precisely describe how the chemosynthetic bacteria provide the necessary energy and nutrients to keep the surrounding ecosystem alive. Verbs like 'sustain', 'support', and 'nourish' are academically precise, fit the formal scientific register of the passage, and clearly convey the idea of maintaining life within the food web.

Step-by-Step Solution

1
Analyze the context of the sentence containing the blank to determine the required part of speech and meaning.
The blank follows the infinitive marker 'to' and precedes the noun phrase 'a diverse community...', indicating that a transitive verb is required. The verb must describe how the energy-producing bacteria at the base of the food web interact with the rest of the ecological community.
Identifying the grammatical role and contextual meaning is necessary to narrow down the vocabulary choices.
2
Evaluate the scientific and academic tone of the passage.
The passage uses formal, scientific language (e.g., 'hydrothermal vents,' 'chemosynthesis,' 'inorganic chemicals'). The word choice in the blank must align with this formal register.
Ensuring the word matches the register prevents stylistic inconsistency, which is a key component of ACT English precision questions.
3
Identify the most precise and clear verb that fits both the grammatical requirements and the scientific context.
The verb 'sustain' (or 'support'/'nourish') precisely communicates the ecological function of keeping the community alive and functioning by serving as the foundation of the food web.
Selecting the most precise term ensures clarity and correctness under ACT standards.

Key Concept

Selecting the most precise and contextually appropriate word to convey a specific meaning while maintaining the correct register and tone.
Question 1617Question

Two positive integers, aa and bb, are such that a<ba < b. The greatest common divisor of aa and bb is 1212, and their least common multiple is 720720. If aa is a multiple of 55 but bb is not a multiple of 55, what is the value of aa?

Show answer & explanation

Answer: 60

Answer

60
By representing a=12xa = 12x and b=12yb = 12y with gcd(x,y)=1\gcd(x, y) = 1 and x<yx < y, the least common multiple constraint gives 12xy=72012xy = 720, which simplifies to xy=60xy = 60. Since aa is a multiple of 55 and bb is not, the factor of 55 in 6060 must belong to xx. Given that x<yx < y and gcd(x,y)=1\gcd(x, y) = 1, the only valid coprime factorization of 6060 where the factor 55 is in xx and x<yx < y is x=5x = 5 and y=12y = 12. This yields a=12×5=60a = 12 \times 5 = 60.

Step-by-Step Solution

1
Express the two numbers in terms of their greatest common divisor (GCD).
a=12xa = 12x and b=12yb = 12y, where gcd(x,y)=1\gcd(x, y) = 1 and x<yx < y.
Since the greatest common divisor of aa and bb is 1212, both numbers must be multiples of 1212, and their remaining parts xx and yy must be coprime to ensure their GCD is exactly 1212.
2
Use the least common multiple (LCM) to find the product of xx and yy.
xy=60xy = 60.
The least common multiple of 12x12x and 12y12y when gcd(x,y)=1\gcd(x, y) = 1 is 12xy12xy. Setting 12xy=72012xy = 720 and dividing by 1212 gives xy=60xy = 60.
3
Identify the constraints on xx and yy based on the divisibility by 55.
55 must divide xx, and 55 must not divide yy.
We are given that a=12xa = 12x is a multiple of 55, which means 55 must be a factor of xx. Since b=12yb = 12y is not a multiple of 55, 55 cannot be a factor of yy.
4
Determine the unique pair (x,y)(x, y) that satisfies all constraints.
x=5x = 5 and y=12y = 12.
The product xy=60xy = 60 has prime factorization 22×3×52^2 \times 3 \times 5. Since gcd(x,y)=1\gcd(x, y) = 1, the factor 55 must belong to xx, and the other prime factors 222^2 and 33 can be distributed. To satisfy x<yx < y, the only possible assignment is x=5x = 5 and y=12y = 12 (since other assignments like x=15,y=4x = 15, y = 4 or x=20,y=3x = 20, y = 3 violate x<yx < y).
5
Calculate the value of aa.
a=60a = 60.
Since a=12xa = 12x and x=5x = 5, we find a=12×5=60a = 12 \times 5 = 60.

Key Concept

Using prime factorizations to analyze greatest common divisors and least common multiples under algebraic and inequality constraints.
Question 1618Question

Point PP is located at 14-14 on a standard number line. Point QQ is located 88 units from point PP in the positive direction. Point RR is located 1111 units from point QQ in the negative direction. What integer represents the location of point RR?

Show answer & explanation

Answer: -17

Answer

The position of point RR is represented by the integer 17-17.
To find the location of point RR, we first determine the location of point QQ by moving 88 units in the positive direction (right) from point PP (at 14-14), which gives 14+8=6-14 + 8 = -6. Next, we find the location of point RR by moving 1111 units in the negative direction (left) from point QQ (at 6-6), which gives 611=17-6 - 11 = -17.

Step-by-Step Solution

1
Calculate the position of point QQ.
6-6
Since point QQ is 88 units from point PP (which is at 14-14) in the positive direction, we add 88 to 14-14: 14+8=6-14 + 8 = -6.
2
Calculate the position of point RR.
17-17
Since point RR is 1111 units from point QQ (which is at 6-6) in the negative direction, we subtract 1111 from 6-6: 611=17-6 - 11 = -17.

Key Concept

Adding and subtracting integers on a number line to find positions relative to a starting point.
Estimated Time:45s
Question 1619Question

Although lacking a brain or central nervous system, the slime mold *Physarum polycephalum* exhibits remarkable problem-solving capabilities. During laboratory experiments, the single-celled organism can navigate complex mazes to locate food. To achieve this, the slime mold leaves a trail of extracellular slime as it moves, creating a physical record of where it has been. Conversely, this externalized spatial memory prevents the organism from wasting energy re-exploring dead ends.

Which choice best transitions from the preceding sentence to the sentence that follows by establishing a logical cause-and-effect relationship?

Show answer & explanation

Answer: Consequently,

Answer

Consequently,
The transition 'Consequently,' correctly establishes the cause-and-effect relationship between the two sentences. The slime mold leaving a physical slime trail acts as its spatial memory (the cause), and as a direct result, the organism avoids wasting energy re-exploring areas it has already visited (the effect).

Step-by-Step Solution

1
Analyze the context and logical connection between the two sentences.
The first sentence explains that the slime mold leaves a slime trail to record its movement, and the second sentence explains that this prevents the mold from entering dead ends.
To choose the correct transition, the relationship between the ideas must be identified.
2
Determine the correct transition type.
Because the second sentence describes the direct outcome or result of the first sentence, a cause-and-effect transition is required.
Identifying the relationship type allows us to eliminate transitions of contrast or illustration.
3
Evaluate the choices based on the target transition type.
The word 'Consequently' denotes cause-and-effect, whereas 'Conversely' and 'On the other hand' denote contrast, and 'For instance' denotes illustration.
This leads to the correct and logical selection.

Key Concept

Selecting transitions that accurately convey the logical relationship (such as cause-and-effect, contrast, or addition) between independent sentences or clauses.
Question 1620Question

Passage Excerpt:

In the summer of 1967, postgraduate student Jocelyn Bell Burnell [1] from a new radio telescope she had helped build. Among the miles of data, she noticed a strange "scruff"—a series of repeating radio pulses that occurred every 1.33 seconds. Although some of her colleagues initially wondered if the signals came from an extraterrestrial civilization, Bell Burnell and her advisor soon realized they had discovered a rapidly spinning neutron star, later named a pulsar.

Which choice most effectively emphasizes the tedious, labor-intensive nature of Bell Burnell's work in analyzing the telescope's output?

Show answer & explanation

Answer: manually scanned miles of paper printouts

Answer

manually scanned miles of paper printouts
The correct option, which mentions manually scanning miles of paper printouts, is the only choice that emphasizes both the hands-on labor ('manually') and the tedious, repetitive volume of the task ('miles of paper printouts') while remaining grammatically correct.

Step-by-Step Solution

1
Analyze the prompt's rhetorical goal.
The goal is to emphasize the tedious and labor-intensive nature of Bell Burnell's data analysis.
Identifying the target criteria allows for systematic evaluation of each option.
2
Evaluate the choices for grammatical correctness and alignment with the prompt's criteria.
Scanning miles of paper printouts manually implies a high volume of work and physical effort, directly matching the prompt's focus. General descriptions of reviewing records or results do not capture this intensity, and placing a comma before a restrictive clause is grammatically incorrect.
Eliminating grammatically incorrect choices and options that do not meet the rhetorical goal leads to the correct answer.

Key Concept

Meeting Specific Rhetorical Goals
Estimated Time:1m 0s
PreviousPage 81 / 278Next
All practice questions — ACT | Examkin