SOLUTION: Suppose a jar contains 19 red marbles and 28 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.

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Question 1199214: Suppose a jar contains 19 red marbles and 28 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 by greenestamps(13198) About Me  (Show Source):
You can put this solution on YOUR website!


Two solutions using standard probability methods....

(1) You are choosing 2 of the 19+28 = 47 marbles; the number of ways to do that is "47 choose 2":
C%2847%2C2%29=%2847%2B46%29%2F%282%2A1%29=1081

The "good" outcomes are when you choose 2 of the 19 red marbles; 19 choose 2:
C%2819%2C2%29=%2819%2A18%29%2F%282%2A1%29=171

The probability is (# good outcomes)/(# of possible outcomes):
ANSWER: 171/1081

(2) Find the probability of getting a red on the first draw and then getting another red on the second draw:
%2819%2F47%29%2A%2818%2F46%29=171%2F1081

Same answer, of course....