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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

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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

by BTGmoderatorDC » Thu Jan 28, 2021 5:12 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. If 2 rocks

by Scott@TargetTestPrep » Wed Feb 03, 2021 9:12 am
BTGmoderatorDC wrote: ↑
Thu Jan 28, 2021 5:12 pm
 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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