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2.    A survey of 320 freshmen. Two hundred fifty students take Math 128, 220 students take English, and 300 students take either Math 128 or English.
a).    Draw a Venn diagram, and label the sections with numbers.


Selecting a student at random, find the probability that:
b).    the student takes Math 128, given that the student takes only one class

c).    the student takes English, given that the student takes Math 128


d).    the student takes Math 128, given that the student takes English


e).    the student takes neither, given that the student does not take Math 128

 
Guest Dec 9, 2015
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2+0 Answers

 #1
avatar+78719 
+5

I'll see what I can do......

 

We need to find the number in the intersection, first....and we have

 

P(M or E)  = P(M) + P(E)  - P(M and E)

 

300  = 250 + 220  - P(M and E)

 

P(M and E)  = 250 + 220 - 300   = 170

 

Here's the Venn diagram :

 

b).    the student takes Math 128, given that the student takes only one class

 

130 students only take  one class.......and 80 of these take Math 128 only....so 80/130  = 8/13

 

c).    the student takes English, given that the student takes Math 128

 

250 students take Math 128......and of these 170 also take English......so  170/250  = 17/25

 

d).    the student takes Math 128, given that the student takes English

 

220 take English.....and of these 170 also take Math 128 ......so    170/220  = 17/22

 

e).    the student takes neither, given that the student does not take Math 128

 

The number not taking Math 128   = 50 plus the 20 taking neither  = 70  ........and there are 20 taking neither [none].....so 20/70  = 2/7

 

[Melody or Alan.....could you check these answers???......I'm not totally confident about these]

 

cool cool cool

CPhill  Dec 9, 2015
 #2
avatar+91039 
0

Yes I got the same answers Chris.   cool

 

I just would have put a box around the 2 circles and put 20 in the box. Just to make the venn diagram right :)

Melody  Dec 10, 2015

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