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There are 15 slate rocks, 20 pumice rocks, and 10 granite rocks randomly distributed in a certain field.

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There are 15 slate rocks, 20 pumice rocks, and 10 granite rocks randomly distributed in a certain field.

by AAPL » Tue Oct 06, 2020 6:19 pm

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There are 15 slate rocks, 20 pumice rocks, and 10 granite rocks randomly distributed in a certain field. If 2 rocks are to be chosen at random and without replacement, what is the probability that both rocks will be slate rocks?

A. 1/3
B. 7/22
C. 1/9
D. 7/66
E. 2/45

OA D
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Re: There are 15 slate rocks, 20 pumice rocks, and 10 granite rocks randomly distributed in a certain field.

by Scott@TargetTestPrep » Sat Oct 10, 2020 2:23 pm
AAPL wrote: ↑
Tue Oct 06, 2020 6:19 pm
 GMAT Prep

There are 15 slate rocks, 20 pumice rocks, and 10 granite rocks randomly distributed in a certain field. If 2 rocks are to be chosen at random and without replacement, what is the probability that both rocks will be slate rocks?

A. 1/3
B. 7/22
C. 1/9
D. 7/66
E. 2/45

OA D
Solution:

The probability of getting two slate rocks is 15/45 x 14/44 = 1/3 x 7/22 = 7/66.

Answer: D

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