Question

If the sum of n terms of an A.P. is 3n² + 5n then which of its terms is 164?

(a) 26th

(b) 27th

(c) 28th

(d) none of these.

Answer 1

Here, the sum of first n terms is given by the expression,

We need to find which term of the A.P. is 164.

Let us take 164 as the n^th term

So we know that the n^thterm of an A.P. is given by,

So,

Using the property,

We get,

Further solving for n, we get

Therefore,

Hence the correct option is (b).