SOLUTION: Still struggling with this one. There are 20 customers. 18 will make a purchase. If three customers are selected, one at a time, what is the probability that all will make a purcha

Question 149737: Still struggling with this one. There are 20 customers. 18 will make a purchase. If three customers are selected, one at a time, what is the probability that all will make a purchase? Instructor says the answer is one of four 1)0.7717, 2) 0.7605 3) 0.8524 or 4)0.8808
Please help
Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
would be interested in seeing the instructor's solution

there are 20C3 (1140) possible groups of 3 in 20 __ some of these groups contain non-purchasers

there are 18C3 (816) possible groups of 3 in 18 __ none of these groups contain non-purchasers

probability of all purchasers is 816/1140 or 0.716 (approx)

if order of selection is thought to be important (permutation vs combination); the result will be the same
RELATED QUESTIONS
In a shop there are 20 customers, 18 of whom will make a purchase. If three customers are (answered by Marth)

18 out of 20 customers make a purchase. If three customers are selected randomly one at a (answered by scott8148)

In a shop there are 20 customers, 18 of whom will make a purchase. If three customers are (answered by Edwin McCravy,stanbon)

In a department store there are 120 customers, 90 of who will buy at least 1 item. If 5... (answered by stanbon)

A fast food restaurant has heard that some of its customers have been dissatisfied with... (answered by stanbon)

Item4 14 points eBookAskPrintItem 4 Exercise 5-26 Steele Electronics Inc. sells... (answered by ikleyn)

According to a survey, only 15% of customers who visited the web site of a major retail... (answered by stanbon)

"A researcher found that 85% of customers who make purchase at a department store are... (answered by stanbon)