GED Mathematical Reasoning TestQuantitative Problem Solving with Rational NumbersEasy
A recipe calls for 1.5 cups of flour for every 2 cups of sugar. If a baker uses 6 cups of sugar, how many cups of flour are needed?
- A3 cups
- B6 cups
- C9 cups
- D4.5 cups
Show answer & explanationAnswer & explanation
Correct answer: D. 4.5 cups
Set up a proportion: 1.5 cups flour / 2 cups sugar = x cups flour / 6 cups sugar. Cross-multiply: 2x = 1.5 * 6. So, 2x = 9, which means x = 4.5 cups of flour.
Why the other options are wrong
- A. This would be the answer if the ratio was 1:2 and sugar was 6 cups.
- B. This would mean a 1:1 ratio, which is incorrect.
- C. This would be the answer if the ratio was 3:2 and sugar was 6 cups.
Proportions
A proportion is an equation stating that two ratios are equal. It can be used to find an unknown quantity when one ratio and part of another are known.
- Ratios compare two quantities.
- Proportions equate two ratios.
- Cross-multiplication is a common method to solve for an unknown in a proportion.
Memory trick: Ratios balanced, unknown found, by cross-multiplying all around.