Question

In the lock (shown on picture), there are ten numbers to choose from the set of (0, 1, ..., 9) and we choose 4 of them. How many ways are there to choose them?

Answer 1

10 000.

Explanation:

If no restriction of repetition is stated, there is an equal possibility of 10 numbers for the 4 slots. So that means, 10^4. Which gives us 10 000.