hard · GMAT Quant
Two nonempty groups A and B contain 25 real numbers in total, and their combined mean is 16. Group A has mean 10 and variance 4, while group B has mean 20 and variance 9. Every number in A is increased by 2, and every number in B is decreased by 3. What is the variance of the resulting 25 numbers? (Variance means the mean of the squared deviations from the mean.)
- 7
- 9
- 25
- 13
- 31
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