Question

the sum of the following AP 2 7 12 to 20​

Answer 1

A. Pis 2,7,12,17

a=2,d=7-2=5,n=4

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

=4/2(2(2)+(4-1)5)

=2(4+15)=2(19)=38

Answer 2

Here a=2,n=20

And d=7−2=5

Sn=2n[2a+(n−1)d]

S20=2/20[2(2)+(20−1)5]=

10(4+19×5)=990

HOPE IT WILL HELPS YOU