If variance of x is 24, then what is the variance of (x+1)/2?
It seems tough since you don't have the data. If you have the data, you could add 1 to each of them then divide by 2. Now you don't have them
(24+1)/2=12.5 ? WRONG
1-Variance of X if added or subtracted by a number, remains the same
2- Variance of X if multiplied or divided by a number, is multiplied or divided by that number squared.
So, let's write (x+1)/2 in this way:
x/2 + 1/2
considering rule #1, we omit the second part, 1/2.
So, now we wanna calculate the variance for x/2.
As rule #2 say, we should divide 24 by 4 (2 squared)solution= 6
Source: my own question. I know it's not a standard GMAT question, but who knows, maybe GMAC decides to continue ever growing difficulty of GMAT by including these easy rules
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