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Bunuel
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A bag of marbles contains twice as many red marbles as blue marbles 17 Oct 2020, 12:33
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91% (01:14) correct 9% (01:24) wrong based on 74 sessions

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A bag of marbles contains twice as many red marbles as blue marbles, and twice as many blue marbles as green marbles. If these are the only colors of marbles in the bag, what is the probability of randomly picking a blue marble from the bag?

(A) 1/6
(B) 2/9
(C) 1/4
(D) 2/7
(E) 1/3
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D
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A bag of marbles contains twice as many red marbles as blue marbles 17 Oct 2020, 12:50
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R=2B
B=2G
R+B+G=7/2B
So probability of chosing a blue marble is B/(7/2B)
=2/7

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A bag of marbles contains twice as many red marbles as blue marbles 17 Oct 2020, 14:37
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Pick numbers that work:

r = 8
b = 4
g = 2

b / Total = 4/14 => 2/7

D
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A bag of marbles contains twice as many red marbles as blue marbles 17 Oct 2020, 19:26
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A bag of marbles contains twice as many red marbles as blue marbles, and twice as many blue marbles as green marbles. If these are the only colors of marbles in the bag, what is the probability of randomly picking a blue marble from the bag?

(A) 1/6
(B) 2/9
(C) 1/4
(D) 2/7
(E) 1/3

Let's denote the number of green marbles as x. Then, the number of blue marbles will be 2x and the number of red marbles will be 4x. Total number of marbles in the bag will be x+2x+4x=7x. Then the probability of randomly picking a blue marble from the bag is equal to 2x/7x=2/7 D)
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A bag of marbles contains twice as many red marbles as blue marbles 19 Oct 2020, 06:30
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Suppose Green Marble = x
Blue Marble = 2x
Red Marble = 4x
Total = 7x

Probability of Blue Marble = \(\frac{2x}{7x}\)
= \(\frac{2}{7}\)

Ans D
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