GMAT Prep - Standard deviation

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GMAT Prep - Standard deviation

by [email protected] » Tue Sep 04, 2007 7:27 pm
The average of 100 numbers is 6, and the standard deviation is D, where D is positive. When added which of the following numbers, the new deviation will be less than D?

A. -6 and 0

B. 0 and 0

C. 0 and 6

D. 0 and 12

E. 6 and 6.

I face difficulty in solving Standard deviation problems.Does anyone have good material on this.
Please solve this question

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by hopefully » Wed Sep 05, 2007 2:42 am
is is 6 and 6

thsi will not add to numerator of the SD formula but will add 2 to the denominator..

hence will decrease it...