From experience, the manager of Kramer's Book Mart knows that 60% of the people who are browsing in the store will make a purchase. What is the probability that among ten people who are browsing in the store, at least three will make a purchase?

1 Answer
MathFact-orials.blogspot.com
Apr 16, 2018

#~~0.98771#

Explanation:

This is a binomial probability question. The general form is:

#sum_(k=0)^(n)C_(n,k)(p)^k(1-p)^(n-k)=1#

or in other words, the sum of all the possible results from a given population (#n#) from all the trials (#k#) with a set probability (#p#) will sum to 1.

Here, we have #n=10# and #p=0.6#.

We can sum up for #3<=k<=10# or we can subtract #0<=k<=2# from 1 to find the probability:

#1-(C_(10,0)(.6)^0(.4)^(10)+C_(10,1)(.6)^1(.4)^(9)+C_(10,2)(.6)^2(.4)^(8))~~1-0.01229~~0.98771#

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