Sets - problem 2

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Sets - problem 2

by venmic » Thu Jun 30, 2011 10:22 pm
Marketing - 30
Sales -50
Leadership - 20

The table above shows the number of MBA students that opted for each of the specified subjects. Although no student has opted for all three subjects, 10 students are in both Marketing and Sales, 7 students are both in Sales and Leadership, and 9 students are in Marketing and Leadership. How many different students have opted for the three different subjects?

answer - 74
Source: — Problem Solving |

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by Frankenstein » Thu Jun 30, 2011 10:42 pm
Hi,
Let
e1 = number of students who opted only 1 course
e2 = number of students who opted only 2 courses
e3 = number of students who opted only 3 courses
We need to find e1+e2+e3
e1+2e2+3e3 = 30+50+20 = 100
given that e3=0
and e2 = 10+7+9 = 26
So, e1+e2+26 = 100 =>e1+e2 = 74
If you can draw Venn diagrams, it will bevery easy.
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by amit2k9 » Thu Jun 30, 2011 10:48 pm
only marketing students = 30 - (10+9) = 11
only sales students = 50 - (10+7) = 33
only leadership students = 20- (9+7) = 4

thus students opting for different subjects = 11+33+4 = 48.
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by venmic » Sat Jul 02, 2011 9:47 am
i did this mistake the answer s 74
amit2k9 wrote:only marketing students = 30 - (10+9) = 11
only sales students = 50 - (10+7) = 33
only leadership students = 20- (9+7) = 4

thus students opting for different subjects = 11+33+4 = 48.