Question

The sum of all natural number between 100 to 200 which are multiple of 

how we solve this

Answer 1

Since number is not specified, we will take 7 as example.

 have to find the sum of 105,112,119,126........196

now lets find total no. of terms in this A.P.

196=105+(n-1)*7

n-1 = 91/7

n=14

now total sum S= 7[2*105 + (14-1)*7]

S= 7[210+91]

S=7*301

S=2107