SOLUTION: 18 of a group of 20 people will purchase from a store. If 3 people are selected one at a time, what is the probability all 3 will buy? I can not find the formula to solve!

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Question 390351: 18 of a group of 20 people will purchase from a store. If 3 people are selected one at a time, what is the probability all 3 will buy? I can not find the formula to solve!
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Hint: This is a binomial problem where p=18%2F20=9%2F10=0.9


So if you want the probability that exactly x people will buy, you would use the formula

(n C x)*(p^x)*(1-p)^(n-x)


where 'n' is the total number of people and n C x is the combination formula

n C x = n!/(x!(n-x)!)


If you need more help, email me at jim_thompson5910@hotmail.com

Also, feel free to check out my tutoring website

Jim