# Thread: Picking Marbles from a bag--Probability

1. ## Picking Marbles from a bag--Probability

Could anyone help me out?

There are 100 marbles in a bag, 50 blue, 40 red, and 10 purple. You draw three times returning a marble to the bag each time you draw (this makes one game). What is the probability of getting 1 purple, 1blue, and 1 red? Purple, then blue, then purple? Red, then blue, then red?

I found out that there are 27 total possibilities, so would it just be # of times that it comes up/27 or would the probability of picking each marble play into this also?

2. P(Blue)=0.5, P(Red)=0.4, P(Purple)=0.1

This is unconditional probability as the events do not affect each other.

P(blue, red, purple once) =(0.5)(0.4)(0.1)=0.02
That is to say:

Blue, Red, Purple = 0.02.
Blue, Purple, Red = 0.02
Red, Blue, Purple = 0.02
Red, Purple, Blue = 0.02
Purple, Blue, Red = 0.02
Purple, Red, Blue = 0.02

So what is the probability of you receiving a purple, blue and red in any order?

3. Oh, so it would be a 12% chance of getting purple, blue and red in any order?

What about the other 2 then?

4. Follow the same format.

As I said above, P(purple) = 0.1 and P(blue) = 0.5

P(Purple, blue, purple) = (0.1)(0.5)(0.1) = 0.005
So just a 0.5% chance. Note that order is important here, so you do not write out the possible combinations.

Have an attempt at the final part yourself now.

5. Then the last one would have an 8/100 chance.

Thank you so much!

6. Originally Posted by led23
Then the last one would have an 8/100 chance.
Yup.