Question

A whole number consists of the digits 2, 4, 6, 8, and 0. If each digit is used only once, how many whole numbers are possible?

Answer 1

Using the digits of 2, 4, 6, 8, and 0 as a number and only using them once, you could possibly have 120 different numbers. You can get this by having a choice of 5 numbers for the first digit, 4 numbers for the second digit and so on...leaving the problem of 5! (five factorial....5x4x3x2x1 = 120)

Answer 2

120 numbers are possible. You have five spots for numbers. 

_ _ _ _ _

Since each digit is used only once, there are 5 possibilities for the first digit, 4 for the next, 3 for the next, and so on. 

5 4 3 2 1

5 x 4 x 3 x 2 x 1 = 120