Question

The first term of finite A.P. is 5 the last term is 45 and the sum is 500. Find the number of terms.

Answer 1

We have,

$a=5,l=45,S_n=500,n=?$

We know that

$S_n=\frac{n}{2}(a+l)$

$500=\frac{n}{2}(5+45)$

$500\times 2=n\times 50$

$n=20$

Hence, this is the answer.