Question

The first and last terms of an A.P. are 1 and 11. If the sum of its terms is 36, then the number of terms will be

Options

• 5

• 6

• 7

• 8

Answer 1

In the given problem, we need to find the number of terms in an A.P. We are given,

First term (a) = 1

Last term (a_n) = 11

Sum of its terms S_n = 36

Now, as we know,

`S_n = (n/2) ( a + l)`

Where, a = the first term

l = the last term

So, we get,

        `36 = (n/2)(1 + 11)`

`36(2) = 12n`

       `n = (36(2))/12`

        n = 6

Therefore, the total number of terms in the given A.P. is  n = 6