If a box contains 4 red marbles, 7 white marbles, and 5 blue marbles. If one is drawn at random, what is the probability that both marbles are white if the draws are made without replacement?


Tammy Gilreath

I assume you mean "if two are drawn at random," not one - correct?

You start with a total of 16 marbles, 7 of which are white. So on the first draw the probability of pulling a white marble is 7/16. If that is successful, then there are only 6 whites left out of the 15 remaining marbles, so the probability of pulling a second white marble is 6/15. Hence the probability of pulling two white marbles in a row without replacement is (7/16)*(6/15).