Question

How many terms of th ap 73,69,66 be taken so that their sum is 897?

Answer 1

AP- 73,69,66
a1=73
d=-4
Sn=897

Sn=1/2[2a+(n-1)d]
897= 1/2[2*73+(n-1)-4]
897=1/2[614+(-4n+4)]
897=1/2[614-4n+4]
897=1/2*2[307-2n+2]
897=309-2n
897-309=-2n
588=-2n
-294=n
Since, no of terms cannot be in negative
Therefore,Number of terms is 294.