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#1 2012-09-16 02:18:57

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

geometry venn diagram help plzzzzz

Hey,

I am like really really confused on how to solve this I uploaded a picture of what I did then am just stuck and confused.


15. 500 students are enrolled in at least two of these three classes: Math, English, and History.  170 are enrolled in both Math and English, 150 are enrolled in both History and English, and 300 are enrolled in Math and History.  How many of the 500 students are enrolled in all three?

A 300
B 330
C 200
D 120
E 90
F 60


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#2 2012-09-16 05:20:32

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,654

Re: geometry venn diagram help plzzzzz

Hi zee-f;


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#3 2012-09-16 07:17:43

zee-f
Member
Registered: 2011-05-12
Posts: 1,220

Re: geometry venn diagram help plzzzzz

I already have the answer F is correct but the thing is I dont get how they got 60 using the Venn digram


One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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#4 2012-09-16 07:27:54

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,654

Re: geometry venn diagram help plzzzzz

Hi zee-f;

I am looking at two solutions to this problem and both of them are algebraic.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#5 2012-09-19 08:41:55

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,532

Re: geometry venn diagram help plzzzzz

hi zee-f

I like to draw a diagram for these questions. (see below)

For three sets there are 8 regions including the outside.  But for your problem you can assume that the three 'only one subject' regions and the outside are all zero.

So call the one you have to find x.

Make up algebraic expressions for the other regions and add them up.

Make an equation by setting this equal to 500.

Solve for x.

Bob

View Image: zeevenn.gif

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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