Question

How many different 4-digit numbers can be formed from the following numbers, 3, 7, 2, and 5, using each digit only once?

Answer 1

You have four digits to place: __ __ __ __

In the first position, you have 4 choices of numbers.

Once the first digit is placed, you have 3 choices left for the second position.

Once the second digit is placed, you have 2 choices left for the third position.

Once the third digit is placed, you have only 1 choice left for the last position.

This gives you 4x3x2x1 = 24 possibilities.