1.  In how many ways can 5 letters be posted in 3 post boxes, if any number of letters can be posted in all of the three post boxes?
A. 5C3
B. 5P3
C. 125
D. 243
E. 32

Answer: Option D

Explanation:

The first letter can be posted in any of the 3 post boxes. Therefore, we have 3 possibilities.

Similarly, the second, the third, the fourth and the fifth letter can each be posted in any of the 3 post boxes.

Each of the 5 letters has 3 possibilities because we can post any number of letters in all of the boxes.

Therefore, the total number of ways the 5 letters can be posted in 3 boxes is :

(3 x 3 x 3 x 3 x 3) = 35 = 243