Question

the sum of 1st 15 terms of 1+3+5....is​

Answer 1

Answer:

1+3+5+......+15.

Here a=1, d=3-1=2, n=15.

We know that

Sn=n/2[2a+(n-1)d].

Sn=15/2[2(1)+(15-1)(2)].

Sn=15/2[2-(14)(2)].

Sn=15/2[2-28].

Sn=15/2[26].

Sn=15×13.

Sn=195.

Answer:- 195.