Question

How many terms of the ap 9,17,25......must be takento give a sum of 636

Answer 1

We know:
sum of ap = n/2(a+(n-1)d)
so,636=n/2(9+(n-1)8)
=636*2=n(9+8n-8)
now u can form a quadratic equation
and solve it..

Answer 2

Refer to the attachment