Question

The number of 4 digit number that can be formed using the digits 0,1,2.3.4,5 that are divisible by 6 when repetition is allowed is

Answer 1

If a 4-digit number is formed by using the digits 1,2,3,4,5 (repitition is allowed )

Thousands, Hundreds and Tens place can be filled up with 5 ways each.

So, a total of 5×5×5 ways to fill these three place.

Now, if the given numbers 1,2,3,4,5 are filled in the unit place, they will form 5 consecutive numbers, out of which only one is divisible by 6.

So, total 4-digit numbers divisible by 6 are 5×5×5×1=125