A shopkeeper sells house numbers. She has a large supply of the digits, 1, 2, 7, and 8, but no other digits. How many different three-digit house numbers could be made using only the digits in her supply?

64.

Step-by-step explanation:

The digits used are 1 , 2, 7 and 8

To make a number of three digits, the digits are repeated.

To make the three digit number

The ones place is filled by 4 ways.

The tens place is filled by 4 ways.

The hundred place is filled by 4 ways.

So, the total number of ways to make a three digit number is 4 x 4 x 4 = 64.