Question

Difficulty: MediumFraction Addition and Subtraction in Context

A painter is mixing a custom green paint. The formula requires mixing blue and yellow paint in a ratio of 11 part blue to 33 parts yellow. He needs exactly 221222\frac{1}{2} gallons of the green paint mixture for a large commercial job. So far, he has poured 1341\frac{3}{4} gallons of blue paint from one can, and 22 quarts of blue paint from another can into the mixing bucket. How many more gallons of blue paint does he need to add to reach the correct amount of blue paint for the entire job?

  1. 3383\frac{3}{8}Answer
  2. B
    5145\frac{1}{4}
  3. C
    323243\frac{23}{24}
  4. D
    1781\frac{7}{8}

Answer

The painter needs 3383\frac{3}{8} more gallons of blue paint.
First, the correct fraction of blue paint is identified from the 1:31:3 ratio, which is 11 part out of 44 total parts (14\frac{1}{4}). The total blue paint needed is 14\frac{1}{4} of 221222\frac{1}{2} gallons, which is 5585\frac{5}{8} gallons. The painter has already poured 1341\frac{3}{4} gallons and 22 quarts (which is 12\frac{1}{2} gallon). Adding these gives 2142\frac{1}{4} gallons poured. Finally, subtracting the poured amount from the total needed (558−2145\frac{5}{8} - 2\frac{1}{4}) leaves 3383\frac{3}{8} gallons.

Step-by-Step Solution

1
Determine the fraction of the mixture that is blue paint.
The ratio of blue to yellow is 1:31:3, meaning there is 11 part blue for every 44 total parts (1+31 + 3). The fraction is 14\frac{1}{4}.
This is necessary to find out how much blue paint is required for the entire 221222\frac{1}{2} gallon mixture.
2
Calculate the total amount of blue paint needed for the job.
14×2212=14×452=458=558\frac{1}{4} \times 22\frac{1}{2} = \frac{1}{4} \times \frac{45}{2} = \frac{45}{8} = 5\frac{5}{8} gallons.
Multiplying the total mixture volume by the fraction of blue paint gives the target amount of blue paint.
3
Convert the quarts of blue paint already poured into gallons.
Since 44 quarts equal 11 gallon, 22 quarts is equal to 24\frac{2}{4} or 12\frac{1}{2} gallon.
All measurements must be in the same unit (gallons) before adding them together.
4
Calculate the total amount of blue paint already poured.
134+12=134+24=154=2141\frac{3}{4} + \frac{1}{2} = 1\frac{3}{4} + \frac{2}{4} = 1\frac{5}{4} = 2\frac{1}{4} gallons.
This finds the combined volume of the two separate pours of blue paint.
5
Subtract the poured amount from the total needed amount.
558−214=558−228=3385\frac{5}{8} - 2\frac{1}{4} = 5\frac{5}{8} - 2\frac{2}{8} = 3\frac{3}{8} gallons.
Subtracting what has been poured from the target amount gives the remaining amount needed.

Key Concept

Fraction addition and subtraction in practical measurement scenarios, including basic unit conversion and proportional reasoning.
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