Situation: When you throw 4 dice at once, the chances all the dice will be divisible by 3 is 1/16

Question: Prove the amount of dice you throw is 4.

Can somebody please explain how the amount of dice is 4?????

Here's how I tried understanding: When you throw 4 dice, there are 5 possible situations you can get all the dice divisble by 3:

1. 3,3,3,3

2. 3,3,3,6

3. 3,3,6,6

4. 3,6,6,6

5. 6,6,6,6

Then I counted all the possible situations you can get when you have 4 dice

(1,1,1,1; 1,1,1,2.....) and that adds up to 24.

So I got that when you spin 4 dice the odds are 5/24 that all the dice will be divisble by 3.

Can someone please help? Thanks