Counting

A basket contains 7 green marbles and 6 red marbles. Two marbles are taken from the basket at random without replacement (i.e., the first marble is not put back before the second marble is drawn). What is the probability that the first marble is green, and that the second marble is red?    

Prob 1st marble green is   7 / 13    

Prob 2nd marble red is      6 / 12    

Prob both happening is     (7 / 13) x (6 / 12) = 42 / 156  reduces to  7 / 26    

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