Question

For an ap the first and the last term sir 13 and 216 respectively common difference is 7 how many terms are there in ap find the sum of the all terms

Answer 1

Last term (A) = 216

First term (a) = 13

common difference (d) =7

A=a +(n-1).d

216= 13 + (n-1).7

n-1 = 203/7

n=29+1=30

sum of all the terms S =

$= \frac{n}{2} (2a + (n - 1).d)) \\ = \frac{30}{2} ((2 \times 13) + (30 - 1).7) \\ = 15.(26 + 203) = 3435$