Question

find the sum of all the three digit number divisible by 4

Answer 1

Three digit numbers are from 100 to 999
divisible by 4 = 100, 104, 108.......996
so, this is an AP with first term 100 and common difference = 4
To find number of terms
996 = [100+(n-1)4]
⇒4n -4 = 896
⇒4n = 900
⇒n = 225
now, sum = (225/2)[100+996] = (225×1096)/2
                = 123300

Answer 2

Three digit numbers are from 100 to 999
divisible by 4 = 100, 104, 108.......996
so, this is an AP with first term 100 and common difference = 4
To find number of terms
996 = [100+(n-1)4]
=4n -4 = 896
=4n = 900
=n = 225
now, sum = (225/2)[100+996] = (225×1096)/2
                = 123300