GRE General TestQuantitative ReasoningEasy
A chemist is preparing a solution. She needs to mix 3 parts of chemical A with 5 parts of chemical B. If she has 400 mL of chemical B, how much chemical A (in mL) does she need?
- A240
- B150
- C200
- D667
Show answer & explanationAnswer & explanation
Correct answer: A. 240
Set up a proportion using the given ratio of chemical A to chemical B, and the known quantity of chemical B, to solve for the unknown quantity of chemical A.
Why the other options are wrong
- B. This is incorrect; likely a miscalculation or incorrect ratio setup.
- C. This results from a misinterpretation of the ratio or calculation error.
- D. This is incorrect; potentially an inverse ratio or incorrect division.
Proportional Reasoning
Using ratios to determine an unknown quantity when a known relationship between two quantities is given.
- Ratios can be written as fractions: a/b = c/d.
- Cross-multiplication is used to solve proportions: ad = bc.
- Ensure units are consistent when setting up proportions.
Memory trick: Ratio's Rule: Set up the fractions, then cross-multiply to solve.