Quote:
Originally Posted by Retake_GMAT
First term a=2, common difference d=2 since even number
therefore sum to first n numbers of Arithmetic progression would be
n/2(2a+(n-1)d)
= n/2(2*2+(n-1)*2)=n(n+1) and this is equal to 79*80
therefore n=79 which is odd
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Completely agree with retake_gmat. PLease post the
OA and source of this question