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by BTGmoderatorRO » Sun Jan 07, 2018 7:55 am
Out of a box that contains 4 black and 6 white mice, three are randomly chosen. What is the probability that all three will be black?

a) 8/125.
b) 1/30.
c) 2/5.
d) 1/720.
e) 3/10

OA is B
What best and suitable method to solve this. An Expert contribution pls.
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by Brent@GMATPrepNow » Sun Jan 07, 2018 8:17 am
Roland2rule wrote:Out of a box that contains 4 black and 6 white mice, three are randomly chosen. What is the probability that all three will be black?

a) 8/125.
b) 1/30.
c) 2/5.
d) 1/720.
e) 3/10
P(all 3 selected mice are black) = P(1st mouse is black AND 2nd mouse is black AND 3rd mouse is black)
= P(1st mouse is black) x P(2nd mouse is black) x P(3rd mouse is black)
= 4/10 x 3/9 x 2/8
= 1/30
= B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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