There are two boxes A and B. In box A, there are 3 red marbles and

Question

There are two boxes A and B. In box A, there are 3 red marbles and 5 green marbles. In box B, there are 2 red marbles and 3 green marbles. Jack rolls the dice. If the result is 1 or 6 then Jack will pick a marble from box A. If the result is neither 1 nor 6 then Jack will pick a marble from box B. What is the probability that the picked marble is green?

A. 1/8
B. 73/120
C. 21/40
D. 5/24
E. 25/56

A. 1/8
B. 73/120
C. 21/40
D. 5/24
E. 25/56

vitaliyGMAT · Answer

Hi again

Events are independent hence: P(A)*P(Green) + P(B)*P(Green) \frac{2}{6} * \frac{5}{8} + \frac{4}{6}* \frac{3}{5} = \frac{146}{6*40} = \frac{73}{120} Answer B.

ScottTargetTestPrep · Answer

We are given that in box A, there are 3 red marbles and 5 green marbles, and in box B, there are 2 red marbles and 3 green marbles. When the die is rolled, if the result is 1 or 6 then Jack will pick a marble from box A, and if the result if neither 1 nor 6 then Jack will pick a marble from box B. We need to determine the probability that a green marble is selected.

Notice that the probability that a green marble is selected is the probability that a green marble is selected from box A or from box B. That is, the probability of selecting a green marble is the probability that it’s selected from box A plus the probability that it’s selected from box B. Let’s start with box A.

P(rolling a 1 or 6) = 2/6 = 1/3

P(selecting a green marble) = 5/8

Thus, the probability of selecting a green marble from box A is 1/3 x 5/8 = 5/24.

Now we can move to box B.

P(not rolling a 1 or 6) = 2/3

P(selecting a green marble) = 3/5

Thus, the probability of selecting a green marble from box B is 2/3 x 3/5 = 2/5.

The probability of selecting a green marble from box A or box B is:

5/24 + 2/5 = 25/120 + 48/120 = 73/120

Answer: B

TheFlash · Answer

Can anyone please explain how the probability of getting green marble in the second condition is 3/5?

hiralk126 · Answer

The total number of marbles in Box B is 5 (2 Red and 3 Green). Therefore the probability of green marble is Green marble/Total marbles in Box B which is 3/5. Hope this helps!

Or19 · Answer

Red 
 Green 
 Tot 
 
  A 
 3 
 5 
 8 
 
  B 
 2 
 3 
 5

Prob. A = 1 or 6 (out of 6) =  \frac{2}{6}  =  \frac{1}{3} 
Prob. B = 2 or 3 or 4 or 5 (out of 6) =  \frac{4}{6}  = \frac{2}{3}

->

\frac{1}{3}*\frac{5}{8}+\frac{2}{3}*\frac{3}{5}=\frac{2}{5}*\frac{5}{24}=\frac{48+25}{120}=\frac{73}{120}

DrHetal · Answer

2/6 x 5/8 + 4/6 x 3/5 =73/120

There are two boxes A and B. In box A, there are 3 red marbles and

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There are two boxes A and B. In box A, there are 3 red marbles and

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