# Probability Question

Hi, can someone help me with this question please.

I started off by finding the different possibilities you could get if you added the results of 3 rolls: 0,2,4,5,6,7,9,10,12,15,17,20,22,25,30

That didn’t pan out well

Original post by subbhy
Hi, can someone help me with this question please.
I started off by finding the different possibilities you could get if you added the results of 3 rolls: 0,2,4,5,6,7,9,10,12,15,17,20,22,25,30
That didn’t pan out well

Youre only interested in the first three cases, so how do they arise and what combinations/probabilities give them?
Original post by mqb2766
Youre only interested in the first three cases, so how do they arise and what combinations/probabilities give them?

I tried doing that but I might be missing a few combos in my list

Eg 0 + 0 + 0 = 0
0 + 0 + 2 = 2

Is there a way to tell how many I should have?
Original post by subbhy
I tried doing that but I might be missing a few combos in my list
Eg 0 + 0 + 0 = 0
0 + 0 + 2 = 2
Is there a way to tell how many I should have?

Youre on the right lines, and thinking of each of the three cases (0,2,4) as a nCr counting or a simple tree should help.
Another line of thinking, which for the most part is the same and quicker (though need some insight).

Spoiler

I'd suggest you work along the method of #2-3 first. I think you know that there is one case missing in #2.

This now becomes a counting exercise. I hope you are well-versed with nCr (since we don't care about ordering here).
(edited 3 days ago)