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# Probability

A class is given a list of 20 study problems from which 10 will be part of an upcoming exam. If a given student knows how to solve 15 of the problems, find the probablility that the student will be able to answer,

a. All 10 questions on the exam
b. Exactly 8 questions on the exam
c. At least 9 questions on the exam

#### Solution Preview

All the possibilities of choosing 10 questions out of 20 problems is 20!/(10!10!).
<br>a. The student can answer all 10 questions, then the 10 questions are chosen from 15 problems that the student knows. There are totally 15!/(10!5!) choices. Thus ...

#### Solution Summary

The solution addresses - A class is given a list of 20 study problems from which 10 will be part of an upcoming exam. If a given student knows how to solve 15 of the problems, find the probablility that the student will be able to answer,

a. All 10 questions on the exam
b. Exactly 8 questions on the exam
c. At least 9 questions on the exam

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