Question

How many 4 digit numbers can be formed from digits 0 2 4 6 5 1 such that each number is divisible by 5 and no repetition is allowed?

Answer 1

Answer: 108

explanation: ->

let the number be ABCD

D can only be 0 or 5 for divisibility by 5

when D = 0

A can have  5 values {2,4,6,5,1}

B can have values one less than A = 4 values

C can have values one less than B = 3 values

Hence total numbers = 5 × 4 × 3 = 60

when D = 5,

A can have 4 values { 2,4,6,1} since 0 will make it 3 digit number

B can have values one less than A + {0} = 4 values

C can have values one less than B = 3 values

Hence total numbers = 4 × 4 × 3 = 48

Sum total = 60 + 48 = 108 numbers