Question

Find the sum of all natural numbers between 100 and 500 which
divisible by 7.

Answer 1

Answer:

17157

Step-by-step explanation:

105,+112......+497

let a= 105

d=7

an= 497

to find n

a+(n-1)d= an

105+(n-1)7= 497

(n-1)7= 497-105

n-1= 392/7

n-1= 56

n=57

now sum we know..

Sn=n/2 ( an+a)

=57/2 (497+105)

57/2(602)

57 x 301

=17,157