Question

The sum of first q terms in ap is 162. The ratio of 6th term to its 13th term is 1:2. Find the first and 15th term of this ap.

Answer 1

162=q/2[2a+(q-1).d]………………(1)

t6/t13=1/2

(a+5d)/(a+12d)=1/2

2a+10d=a+12d

a=2d………………….(2)

t15=a+14d

= 2d+14d=16d ,

First term(a)= 2d

15th term = 16d.