Question

find the sum of all natural numbers between 250 and 1000 which are exactly divisible by 3

Answer 1

In AP

first no = 252 and last number is 999 which divisible by 3

let total no be n

so

999=252+(n-1)3 (By using AP)

n=250

By using Sn=(n/2){2a+(n-1)d}

solve

then 156375