Infamous Marbles

I saw this partially explained on another page, but the explanation was incomplete.

A bag contains four blue marbles, three white marbles, and six red marbles. Three marbles are selected from the bag. What is the probability they are all red? All of the same color?

Thank you!

apple said:

I saw this partially explained on another page, but the explanation was incomplete.

Click to expand...

Please post a link to that page. :cool:

There are, originally, 13 marbles in the bag, 6 of which are red. The probability the first marble drawn is red is 6/13. That leaves 12 marbles in the bag, 5 of which are red. The probability the second marble drawn will be red is 5/12. That leaves 11 marbles in the bag, 4 of which are red. The probability third marble drawn will be red is 4/11. The probability all three will be red is the product of those.

You can do the same thing to find the probability all three are blue or all three are white. The probability of the three marbles being the same color is the sum of those.