Probability question

Question

Suppose a jar contains 5 red marbles and 35 blue marbles. If you reach in the jar and pull out 2 marbles at random at the same time :Find the probability that both are red.

The answer in the homework key is 1/78 =.013

Answer 1

Hi Ralph...there are various ways to do this depending on what they've taught in your course, but the most basic way is to consider that the probability the first marble being red is 5 out of 40, and the second one (once the first is taken) is 4/39 since you took a red one already. Multiply 5/40 x 4/39 and there you go!