Question

Which term of the A.P. 3, 15, 27, 39, ... will be 120 more than its 21^st term?

Answer 1

In the given problem, let us first find the 21^st term of the given A.P.

A.P. is 3, 15, 27, 39 …

Here,

First term (a) = 3

Common difference of the A.P. (d) =12

Now, as we know,

So, for 21^st term (n = 21),

Let us take the term which is 120 more than the 21^st term as a_n. So,

Also,

Further simplifying, we get,

Therefore, theof the given A.P. is 120 more than the 21^st term.