gmat prep

[vaivish]

help

[varunrajwade]

Let the smallest be x, then the series is x,x+1,.....,x+9,x+10.

i. The average of first 9 is 7, so sum of them is 9*7 = 63. First 9 from the series mean x,x+1,...,x+8. So we have a 9 number AP with the smallest number as X and the difference between each as 1.

Sum of n series AP (S) = (2a+(n-1)*d)*n/2, where a = smallest number in series and d is difference.

Equating S to 63, we can solve for x. Hence (i.) is sufficient and same for (ii). Hence Either of them.

[cubicle_bound_misfit]

IMO D

in a series when odd number of consecutive terms are arranged from least to geratest

AM = median

so stmt 1 :

Average of first 9 int is 7.

hence series is 3 4 5 6 7 8 9 10 11 ---> complete series 12 13
hence Average 8 ---Suff

Stmt 2

average of last 9 int is 9. same way the series can be determined ---SUFF

ans is D.
let me know if this is correct.

regards,