Suppose a jar contains 17 red marbles and 39 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.

Answer 1

Pr(R) =17/(17+39) = 17/56

Pr(2nd R) = (17-1)/(56-1) = 16/55

Pr(2R) =Pr(R)Pr(2nd R) = 17/56 x 16/55 = (17)(16)/(56)(55) 17(2)/7(55)=34/385

= about 8.83% probability of 2 reds