Question

Find the number of natural numbers between 250 and 1000 which are exactly divisible by 3.

Answer 1

Clearly the numbers between 250 and 1000 which are divisible by 3 are $252,255,258,...999.$

$\therefore T_n=999=a+[n-1]d$

$999=252+[n-1]3$

$333=84+n-1$

$\therefore n=333-83=250$