geometry homework

Question

A bag contains 2 red, 5 blue, and 2 white marblesFind the probability of randomly picking a red marble, keeping the marble, and then picking a blue marble.

a. 10/81

b. 1/9

c. 5/36

d. 7/8

Answer 1

There are 9 marbles, 2 red, so probability of first picking a red marble is 2/9. Then there are 8 marbles left and 5 blue marbles, so probability of next picking a blue marble is 5/8. Probability of both events happening is 2/9 * 5/8 = 10/72 = 5/36 (c).