GRE General TestQuantitative ReasoningEasy
A painter is mixing a custom color. He starts with 3 liters of blue paint and 2 liters of yellow paint. If he wants to maintain the same ratio of blue to yellow paint but needs a total of 25 liters of the custom color, how many liters of yellow paint will he need?
- A15 liters
- B12 liters
- C8 liters
- D10 liters
Show answer & explanationAnswer & explanation
Correct answer: D. 10 liters
The initial ratio of blue to yellow paint is 3:2. This means for every 5 liters of mixed paint (3 blue + 2 yellow), 2 liters are yellow. To find the amount of yellow paint needed for 25 liters, set up a proportion: 2/5 = x/25, which yields x = 10.
Why the other options are wrong
- A. This would be the amount of blue paint needed, not yellow.
- B. This is incorrect; it does not maintain the original ratio.
- C. This would be the amount of yellow if the ratio was 2:3 yellow to blue, which is incorrect.
Ratio and Proportion
A ratio compares two quantities, while a proportion states that two ratios are equal, often used to find an unknown quantity.
- Ratios can be written as a:b, a/b, or 'a to b'.
- A proportion is an equation that sets two ratios equal.
- Cross-multiplication is a common method to solve proportions.
Memory trick: Ratios are like recipes, keep the ingredients proportional.