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1. There are 43 cars that start in every Nascar Sprint Cup race. How many ways can they place in the top 5 at each race?



2. There are 102 students in John's freshman seminar class at SUNY Oneonta. The professor tells her students she will be assigning a project in which the students will work in pairs and that she will be selecting the pairs of students. How many pairs of students are possible?

Respuesta :

Question 1)

Total Number of Cars = 43
Number of positions = 5

We have to arrange the cars for first 5 positions. This is a problem of permutations and is equivalent to form arrangements of 5 objects from 43 objects. 

So, the number of ways to place the top 5= 43P5

[tex]= \frac{43!}{(43-5)!} \\ \\ = \frac{43!}{38!} \\ \\ =115511760[/tex]

Thus, there are 115511760 ways to place the 43 cars in top 5.

Question 2)

Total number of students = 102
Number of students that should be together = 2

Making pairs from a group of students is equivalent to making combinations. So this is a problem of combinations and is equivalent to forming combination of 2 objects from 102.

So, the number of pairs that can be formed = 102C2
[tex]= \frac{102!}{2!*100!} \\ \\ =5151[/tex]

This mean with 102 students 5151 pairs of students are possible.

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