Question

In how many ways can 5 leters be posted in 3 boxes.If any number of letters can be posted in all of the three post boxes

Answer 1

The first letter you take, can be posted in any of the 3 letter boxes. So you have a total if 3 choices for the first letter.

Now, the question says that any number of letters can be posted in one box.

So for the 2nd letter too, you have 3 choices.

Same for the 3rd, 4th and 5th letters.

So you have a total of 3x3x3x3x3 = 243 choices