Question

Which term of the AP 3,8, 13,18,…. Will be 55 more than its 20^th term?

Answer 1

Here, a = 3 and d = (8-3) = 5
The 20^th  term is given by 

`T_20 = a + (20-1) d = a+ 19d = 3+ 19xx5 = 98`
∴ Required term = (98 + 55)  = 153

Let this be the n^th   term.

Then T_n = 153

⇒ 3 +(n-1 ) × 5 = 153 

⇒ 5n = 155

⇒ n= 31 

Hence, the 31^st  term will be 55 more than 20^th  term.