Question 1184001
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Out of 20 students in a statistics class 3 students are failing in the course. If 4 students from the class 
are picked up at random what is the probability that one of the failing student will be among them
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    P = {{{(C[3]^1*C[20-3]^3)/C[20]^4}}} = {{{(C[3]^1*C[17]^3)/C[20]^4}}} = {{{(3*680)/4845)}}} = {{{8/19}}} = 0.4211.     <U>ANSWER</U>


The denominator is the number of different quadruples to choose from 20 students - the space of events.


The numerator is the number of those quadruples, that consist of one of 3 failed students and three of remaining 17 students.
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Solved.