Question

Difficulty: MediumAlgebraic Word Problems and Equation Modeling

A craft brewery produces two specialty beverages, Batch A and Batch B, using two primary ingredients: hops and malt. To produce 1 barrel of Batch A, the facility requires 4 kilograms of hops and 10 kilograms of malt. To produce 1 barrel of Batch B, the facility requires 6 kilograms of hops and 15 kilograms of malt. Let aa represent the number of barrels of Batch A produced and bb represent the number of barrels of Batch B produced in a week, where a>0a > 0 and b>0b > 0. The total mass of hops used is HH kilograms, and the total mass of malt used is MM kilograms. Which of the following statements must be true for any valid production quantities of aa and bb? Select all that apply.

  1. 2M=5H2M = 5HAnswer
  2. M>HM > HAnswer
  3. C
    3H2M=03H - 2M = 0
  4. D
    The ratio of total malt used to total hops used, MH\frac{M}{H}, depends on the specific values of aa and bb.
  5. E
    If H=120H = 120, then the number of barrels of Batch A produced (aa) must be equal to 15.

Answer

The statements 2M=5H2M = 5H and M>HM > H must both be true.
Expressing H=4a+6b=2(2a+3b)H = 4a + 6b = 2(2a + 3b) and M=10a+15b=5(2a+3b)M = 10a + 15b = 5(2a + 3b) reveals that M=2.5HM = 2.5H, or equivalently 2M=5H2M = 5H. Because HH is strictly positive for positive values of aa and bb, M=2.5HM = 2.5H also guarantees that M>HM > H.

Step-by-Step Solution

1
Set up algebraic equations for total hops (HH) and total malt (MM) in terms of aa and bb.
H=4a+6bH = 4a + 6b and M=10a+15bM = 10a + 15b.
Each barrel of Batch A uses 4 kg hops and 10 kg malt, while each barrel of Batch B uses 6 kg hops and 15 kg malt.
2
Factor common numerical terms from both algebraic expressions.
H=2(2a+3b)H = 2(2a + 3b) and M=5(2a+3b)M = 5(2a + 3b).
Factoring isolates the common linear factor (2a+3b)(2a + 3b) present in both quantities.
3
Calculate the ratio MH\frac{M}{H} and clear fractions to find the invariant linear equation.
\frac{M}{H} = \frac{5(2a + 3b)}{2(2a + 3b)} = \frac{5}{2} \implies 2M = 5H.
Since a>0a > 0 and b>0b > 0, (2a+3b)0(2a + 3b) \neq 0, so the variable terms cancel completely.
4
Evaluate the inequality relationship between MM and HH.
M=2.5H    MH=1.5H>0    M>HM = 2.5H \implies M - H = 1.5H > 0 \implies M > H.
Because a,b>0a, b > 0, H>0H > 0, making 2.5H2.5H strictly greater than HH.

Key Concept

Linear Equation Modeling and Proportional Invariants
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