GRE General TestQuantitative ReasoningMedium
A quality control engineer is inspecting a batch of 600 components. He finds that 5% are defective. Of the defective components, 20% can be repaired. How many components can be repaired?
- A60
- B30
- C12
- D6
Show answer & explanationAnswer & explanation
Correct answer: D. 6
First, find the number of defective components: 600 * 0.05 = 30 components. Then, find how many of these can be repaired: 30 * 0.20 = 6 components.
Why the other options are wrong
- A. This is 10% of the total or 20% of 300.
- B. This is the total number of defective components, not the repairable ones.
- C. This would be 20% of 60, or 10% of 600.
Nested Percentages
Calculating a percentage of a quantity, and then calculating another percentage of that resulting quantity.
- Involves sequential percentage calculations.
- Each percentage is applied to the result of the previous step.
- Order of operations is crucial.
Memory trick: First a percentage of the total, then another percentage of that sub-total!