Question

How many ways 4 letters can be posted in 4 different letter boxes?

Answer 1

Hi!

Among the 4 boxes, 4 letters can be posted in the first box in 4 ways.

After filling up the letter in the first box, the remaining 3 letters can be posted in the second box in 3 ways. Similarly, in last two boxes the remaining letters can be posted in 2 and 1 ways respectively.

Thus, the ways of posting letter in these boxes = 4 × 3 × 2 × 1 = 24.

Let the boxes