Question

How many four-digit even numbers can be formed using the digits 3,4,7,8 if digits may be repeated?

Answer 1

128

Explanation:

Using the digits, any number ending with the 4 or the 8 will be even.

For a number ending in the 4, the other three digits can be any one of the 4 numbers we are allowed. And so there are:

`4^3=64` numbers that can be made when ending in 4.

The same is true for when the number ends in 8.

And so, in total, we have `64+64=128` numbers possible.