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Answer is A
We can use the following formula for two overlapping groups:chiphipoke wrote:Of the 20 members of a kitchen crew, 17 can use the meat-cutting machine, 18 can use the bread-slicing machine, and 15 can use both machines. If one member of the crew is to be chose at random, what is the probability that the member chosen will be someone who cannot use either machine?
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A note to those who are unfamiliar with the "(Double) Matrix Method": This technique can be used for most questions featuring a population in which each member has two characteristics associated with it.theCodeToGMAT wrote:Use a Matrix Method..
Black ones are from question
Green ones are implied
Red Box is what we need to find.
[spoiler]{A}[/spoiler]
chiphipoke wrote:Of the 20 members of a kitchen crew, 17 can use the meat-cutting machine, 18 can use the bread-slicing machine, and 15 can use both machines. If one member of the crew is to be chose at random, what is the probability that the member chosen will be someone who cannot use either machine?
This question is from GMATPrep's Exam Pack 3 and I cannot solve it for the life of me. Please provide an explanation. Thanks!
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Answer is A