GRE General TestQuantitative ReasoningEasy
A data analyst is examining a set of scores: 10, 15, 20, 25, 30. If each score in the set is increased by 5, and then doubled, what is the new mean of the set?
- A70
- B30
- C50
- D60
Show answer & explanationAnswer & explanation
Correct answer: D. 60
First, calculate the original mean of the set. Then, apply the transformations (add 5, then double) to the original mean to find the new mean.
Why the other options are wrong
- A. This results from doubling each number first, then adding 5, or other miscalculations.
- B. This is the original mean plus 5, but not doubled.
- C. This is the original mean (20) plus 5 (25), then doubled incorrectly (50).
Effect of Transformations on Mean
When a constant is added to or subtracted from each value in a dataset, the mean changes by that constant. When each value is multiplied or divided by a constant, the mean changes by that constant factor.
- If x' = x + c, then mean' = mean + c.
- If x' = x * c, then mean' = mean * c.
- These properties simplify calculations for transformed datasets.
Memory trick: Mean's Mirror: Whatever you do to each number, the mean does too.