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In a class of 28 students, the teacher selects four people at random to participate in a geography contest. What is the probability that this group of four students includes at least one of the top three geography students in the class? Express your answer as a common fraction.

 Apr 6, 2022
 #1
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The probability =  1 minus  the probability that none of the top three geography students are selected  =

 

1 -   (any group of 4 that does not include the top three students)  / ( the total possible groups of four)

 

1 -  C(25 , 4)  / C (28 , 4)   =

 

1 -  12650  / 20475  =

 

1 - 506 / 819  =

 

313 / 819

 

cool cool cool

 Apr 6, 2022

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