Question

Find the sum of all multiples of 7 lying between 300 and 700.​

Answer 1

Step-by-step explanation:

Here a series will be formed as 301, 308, 315, ...........700

So we have the first term a = 301 and d = 7 and last term l = 700

700 = 301+(n-1)7

399 = 7n-7

406=7n

n = 58

Sum = n/2(a+l)

Sum = 58/2(301+700)

= 29 x 1001

= 29029

Answer 2

Difference=700-300=400

Series formed = 301, 308, 315, ...........700

First term a = 301 and d = 7 and last term l = 700

700 = 301+(n-1)7

399 = 7n-7

406=7n

n = 58

Sum = n/2(a+l)

Sum = 58/2(301+700)

= 29 x 1001

= 29029