Question

The lock on a safe requires a three-digit code to open it. The three digits must each be a number from 0-9 (10 possible numbers). Each number cannot be used more than once in the code. How many codes could there be?
A.1,000
B.720
C.30
D.120

Answer 1

The correct answer is Choice B: 720.

To solve this, you have to use the Fundamental Counting Principal. You find the total number of options for each of the digits, then multiply them together.

For the first one, there are 10 options, then 9 options and finally 8 options.

10 x 9 x 8 = 720