Question

If 7 time of 7th term of an A.P is
equal to & 11 time
time of its 11th term
then what is the 18th term of this AP​

Answer 1

Answer:

let a = first term and d=common difference.

According to question,

7a7 = 11 a11

=>7(a+6d) = 11(a+10d)

=> 7a-11a = 110d-42d

=> -4a = 68d

=>a = -17d ......(1)

Now , a18 = a +17d

but a = -17 d ..by (1)

so put this value , we get,

a18=-17d +17d =0

hope it helps you