Question

find the sum of first 23 terms of the arithmetic progression 2,7,12​

Answer 1

Answer:

First term(a)= 2, Common difference(d)=7-2=5

No. of terms(n)=23

Therefore,

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

=>S23= 23/2{4+22×5}

= 23/2×114=23×57

=1311