Question

First and last term of AP is respectively 17 and 35 and common difference is 9, find total number of terms In an AP find sum of total number of terms​

Answer 1

First term 'a'=17,

Last term 'l'=35,

Common difference 'd'=9 (given)

l=a+(n-1)d

35=17+(n-1)9

9n=27

n=3

so, total number of terms is 3.

sum of all terms S=n/2(a+l)

S=3/2(17+35)

S=78

Therefore, sum of all the terms is 78.