GED Mathematical Reasoning TestQuantitative Problem Solving with Rational NumbersMedium
A recipe requires 3/4 cup of milk for every 2 cups of flour. If a baker uses 6 cups of flour, how many cups of milk are needed?
- A2 1/4 cups
- B3 cups
- C4 1/2 cups
- D1 1/2 cups
Show answer & explanationAnswer & explanation
Correct answer: A. 2 1/4 cups
Set up a proportion: (3/4 cup milk) / (2 cups flour) = (x cups milk) / (6 cups flour). Cross-multiply: 2x = (3/4) * 6. 2x = 18/4 = 4.5. x = 4.5 / 2 = 2.25. Convert 0.25 to 1/4, so 2 1/4 cups of milk are needed.
Why the other options are wrong
- B. This would be if the ratio was 1:2, not 3/4:2.
- C. This is an overestimation, possibly an incorrect multiplication or division.
- D. This would be if the flour amount was 4 cups.
Proportions with Fractions
A proportion states that two ratios are equal. When one of the ratios involves a fraction, set up the proportion and use cross-multiplication to solve for the unknown variable.
- Set up as (a/b) = (c/d).
- Cross-multiply: a*d = b*c.
- Solve for the unknown variable.
- Convert improper fractions to mixed numbers if needed.
Memory trick: Equal ratios, cross-multiply, find the missing piece.