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

This is assuming no replacement.

First red marble = 5/9

Second red marble = 4/8

With replacement, the second red marble = 5/9

The probability of both/all events occurring is found by multiplying the individual events.