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A box contains 5 green balls, 3 black balls and 2 red balls. If 2 bal
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12 Nov 2024, 00:20
12 Nov 2024, 00:20
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A box contains 5 green balls, 3 black balls and 2 red balls. If 2 balls are taken out of the box successively without replacement, what is the probability that the two balls are red?
A. 1/45
B. 2/45
C. 1/15
D. 4/45
E. 1/9
A. 1/45
B. 2/45
C. 1/15
D. 4/45
E. 1/9
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Re: A box contains 5 green balls, 3 black balls and 2 red balls. If 2 bal
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15 Nov 2024, 16:38
15 Nov 2024, 16:38
1
5 green balls, 3 black balls, and 2 red balls (10 balls total)
Ball grab #1. Probability that the first ball taken out of the box is red = 2/10 (out of all the balls, 2 are red)
To successfully pull two balls in a row that are red, Ball Grab #1 must be red. The ball is not replaced, so there are 9 balls left in the bag and only 1 red ball is left in the bag (since we pulled the other red ball in ball grab #1).
Ball Grab #2. Probability that the 2nd ball taken out of the box is red = 1/9.
Multiply these probabilities together:
(2/10) x (1/9) = 9/20 (simplified to 1/45 to match the answer choices).
Answer is A
Ball grab #1. Probability that the first ball taken out of the box is red = 2/10 (out of all the balls, 2 are red)
To successfully pull two balls in a row that are red, Ball Grab #1 must be red. The ball is not replaced, so there are 9 balls left in the bag and only 1 red ball is left in the bag (since we pulled the other red ball in ball grab #1).
Ball Grab #2. Probability that the 2nd ball taken out of the box is red = 1/9.
Multiply these probabilities together:
(2/10) x (1/9) = 9/20 (simplified to 1/45 to match the answer choices).
Answer is A
gmatclubot
Re: A box contains 5 green balls, 3 black balls and 2 red balls. If 2 bal [#permalink]
15 Nov 2024, 16:38
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