Question

.)A bag has 7 red marbles, 8 blue marbles and 3 black marbles. What is the probability of picking a blue marble, replacing it, and then picking a red marble? Answer a. 14/81 b. 7/108 c. 2/27 d. 1/9 2.)A bag has 7 red marbles, 8 blue marbles and 3 black marbles. What is the probability of picking a black marble, replacing it, and then picking a red marble? Answer a. 2/27 b. 7/108 c. 14/81 d. 1/9

Answer 1

Choice A. 14/81 
Possible outcomes = total number of marbles = 18 
P (1st blue) = 8/18 = 4/9 
P (2nd red with replacement of blue) = 7/18 
P (both) = (4/9) * (7/18) = 28/162 = 14/81 

Choice B. 7/18
Possible outcomes = total number of marbles = 18 
P (1st black) = 3/18 = 1/6 
P (2nd red with replacement of black) = 7/18 
P (both) = (1/6) * (7/18) = 7/108