In how many ways can 4 letters be posted in 5 letter boxes?

Explanation

Since each letter can be posted in any one of the four letter boxes.

So, a letter can be posted in `4` ways.

Since there are `5` letters and each letter can be posted in `4` ways.

So, total number of ways in which all the five letters can be posted `=4×4×4×4×4=``4^5`