A baby presses the ten numbers (zero through nine) on a phone dial pad once each. How many different number sequences could she have dialed?
The first number the baby presses could be any of the 10 keys - which gives us 10 choices.
The second number pushed can be any of the 9 remaining keys - and so 9 choices.
The third number pushed can be any of the 8 remaining keys - and so 8 choices.
And so on, down to the last key. We can multiply all these choices together: