Question

How many three-digit numbers are divisible by $7$?

Answer 1

First three digit number divisible by 7 is $105$ and last three digit number divisible by $7$ is $994$

This is an AP with first term as 105 and last term as 994 and d=7.

$994=105+(n-1)\times 7$

$n-1=127$

$n=128$