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YOUR SIGNATURE (10) There are 24 students in this class. Eight of the students a

ID: 3323536 • Letter: Y

Question

YOUR SIGNATURE (10) There are 24 students in this class. Eight of the students are from 1B are from Queens, five are from the Bronx and the rest are from places not worth mentioning. YOU DO NOT NEED TO SIMPLIFY YOUR ANSWER. (a) (4 pts) How many ways can I choose 10 of you so that six come from Brooklyn and 4 come from the Bronx? (b) (4 pts) Final project presentations are next Tuesday. Assuming each of you are presenting alone, how many ways can I arrange the order of presentation? (c) (4 pts) I plan on failing exactly 4 of my students. What is the probability that they will all be from Brooklyn?

Explanation / Answer

Given

Total number of students =N=24

No.of students from Brooklyn=n1=8

No.of students from queens=n2=6

No.of students from Bronx=n3=5

No.of students from places not mentioned=n4=5

A)

We have to select 10 students ,so that 6 from Brooklyn and 4 from Bronx

So

We can choose 6 from Brooklyn (out of 8 ) in 8C6 ways

Similarly we can choose from Bronx (out of 5) in 5C4 ways

So total number of ways =8C6*5C4=28*5=140

B)

Since here total 24 different students so we can arrange them in "N!" Ways

So

No.of possible ways =24!

C)

Since choosing four from Brooklyn is possible in 8C4 ways

While there is 24C4 ways of selecting 4 students

So Probability=8C4/24C4