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A bag contains nine blue marbles and three red marbles. You draw three marbles randomly without replacement what is the probability of drawing three blue marbles.

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Hamilton1757
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

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