There are 4 black marbles and 5 red marbles in a bag. If you reach in and randomly select 2 marbles, what is the probability that both are red? Explain your reasoning.

Answer 1

First marble = 5 out of 9 chances (5 reds, total of 9 marbles)
Second marble = 4 out of 8 chances (4 reds, total of 8 marbles left)

Probability = 5/9 x 1/2 = 5/18 = 27.78%