Question

for a given Ap 2, 7 , 12 ,17 ------ sum of how many terms is 990​

Answer 1

Let a be the first term and d be the common difference.

Given series is 2,7,12,17... 990.

Here,

= > a = 2, n = 990

d = 7 - 2 = 5.

We know that sum of n terms of an AP sn = (n/2)[2a + (n - 1) * d]

= > (990/2)[2(2) + (990 - 1) * 5]

= > 495[4 + (989) * 5]

= > 495[4949]

= > 2449755.

Hope this helps!