Question

find the sum of integers between 1 and 200 that are divisible by 3 and 5.​

Answer 1

Answer:

The integers which are divisible by both 3 and 5

in between 1 and 200 are 15,30,45,60,.............195.

a=15 , d=15,

let 195 be nth term of the AP

an=a+(n-1)d

195=15+(n-1)15

195-15=(n-1)15

180/15=n-1

n-1=12

n=12+1

n=13

Sn=n/2[a+l]

S13=13/2[15+195]

=13/2×210

=13×105

=1365

Sum of integers between 1-200 which are divisible by both 3 and5 is 1365