Question

What is the 25th term of the arithmetic series 9, 15, 21, … ?

Answer 1

`147`

Explanation:

Let `(x_n)=(9, 15, 21, 27, .......)` be the arithmetic sequence.

The common difference is `d=x_(n+1)-x_n=6`.
The first term is `a=9`.

The general term is given by `x_n=a+(n-1)d`.

`therefore x_25=9+(24-1)*6`

`=147`