Question

Your bike lock has 4 digits numbered 0 to 9. Find the total number of possible combinations for the lock?

Answer 1

10000

Explanation:

From 0 to 9 is 10 possibilities for each digit. I like to picture it like this:

There are four spots, one for each digit:

__ __ __ __

Each has ten possibilities:

_10_ _10_ _10_ _10_

Because these are independent events, we multiply them:

_10_ x _10_x _10_x _10_

The answer is 10^4 or 10000!