How many five digit numbers can be formed for the set { 0,1,2,3,4,5,6,7,8,9} if zero cannot be the first digit and the given condition for each is to be satisfied?

Question

A. Repetitions are allowed and the number must be even.
B. Repetitions are allowed and number must be divisible by 5.
C. The number must be odd and less than 40.000 with repetition allowed.

Answer 1

a) 9*10*10*10*5

b) 9*10*10*10*2
c) 9*10*10*10*5, now make it less than 40,000, so =3*10*10*10*5