Question

How many three-digit numbers can you make if you are not allowed to use any other digits except 1 and 2? (You may use 1 and 2 in a number more than once or not at all!)

Answer 1

The first digit can be 1 or 2.

For each one ...

The second digit can be 1 or 2.

For each one ...

The third digit can be 1 or 2.

That's (2•2•2)= 8 different possibilities.