Two marbles are drawn without replacement from a box with 3 white, 2 green, and 1 blue marble. Find the probability

Question

a) that both marbles are white?

b) that you draw a green and a white marble?

Answer 1

Assume we are sampling without replacement.

a) There are 3 white marbles and 6 total marbles. The chances are 3/6 you will draw a white marble on the first draw and 2/5 you will draw a white marble on the second draw. To get a white marble on both draws the chance is 3/6 * 2/5 = 6/30 = 1/5.

b) You can either draw a green marble then a white marble or a white marble and a green marble.

To draw green then white is 2/6 * 3/5 = 6/30 = 1/5

To draw white then green is 3/6 * 2/5 = 6/30 = 1/5

Chance of either = 2/5.