Question

A 4digit number greater than 5000 are randomely formed from the digit 0,1,3,5 and 7 what is the probability of forming a number divisible by 5 when 1. The digit are repeated 2. The repetition of digit is not allowed

Answer 1

5^2×2^2 when repetitions are allowed

and when repeating not allowed then 1.4.3.1+1.4.3.1