Question

how many three digit number are divisible by 7

Answer 1

The the three digit number divisible 7 is 105, 112, 119,........, 994

A=105
D=112-105=7
An=l=994

An=A+(n-1)D
=>994=105+(n-1)7

=>994=105+7n-7

=>994-105=7n-7

=>889+7=7n

=>7n=896

=>n=128

Answer 2

(a=105) is the first three digit number divisible by 7
(an=994) is the last three digit number divisible by 7
hope this helps