9 blue marbles
-------------------
3 red marbles
First time you draw a marble and you want it to be blue
You have 12 marbles in all.
If you draw a marble out the first time, the probability that it will be blue is 9/12.
We do not put the marble back. So now we have 11 marbles in all. And 8 blue.
8/11
We do not put that one back.
So we have 10 marbles let and 7 blue.
7/10.
Then we multiply each of these.
9 8 7
--- x --- x ---
12 11 10
9 * 8 * 7 = 504
12 * 11 * 10 = 1320
504/1320 = 0.38 (rounded)
There is a 38% probability that when you draw 3 marbles without replacement they will be all be blue.
Hope this helps you! (:
-Hamilton1757
