Question

Find all number between 100 and 900 which are divisible by 11

Answer 1

11×11=121

then 11×81=891 so there are 80 number divisible buy 11

Answer 2

A1=110

An=891

d=11

An=A+(n-1)d

891 = 110+(n-1)*11

891 -110 = 11n-11

781 + 11= 11*n

n = 792 / 11

n = 71

hence there will be 72 numbers between 100 and 900 when they are divided by 11