Question

A jar contains two red marbles, three green marbles, ten white marbles and no other marbles. two marbles are randomly drawn from the jar without replacement. what is the probability that these two marbles drawn will both be red? express your answer as a common fraction.
the denominator HAS to be 15C2
but what's the numerator?

Answer 1

Since there are only 2/15 red marbles in the jar, to draw the first marble it would be a 2/15 chance, the next draw would only have 14 marbles, and only 1 red marble, giving you a 1/14 chance. Then you would just need to multiply those two together giving you 2/210, which you can simplify to 1/110