SOLUTION: In a shop there are 20 customers, 18 of whom will make a purchase. If three customers are selected, one at a time, at random, what is the probability that all will make a purchase?
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Question 206208: In a shop there are 20 customers, 18 of whom will make a purchase. If three customers are selected, one at a time, at random, what is the probability that all will make a purchase? Answer by Marth(57) (Show Source):
You can put this solution on YOUR website! This is the same as selecting 3 customers without replacement and finding the probability that each one will make a purchase.
The probability of the 1st customer making a purchase is
But for the 2nd customer, after having selected the 1st customer without replacement, the probability is because you remove one customer that has made a purchase.
Do the same for the 3rd customer:
Now multiply them together: =
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