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Set Theory

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by msd_2008 » Sat Dec 06, 2008 4:48 am
Q. There are 50 students, 22 take accounts, 15 take finance & 14 take marketing. 9 take exactly 2 courses & 1 takes all 3. How many of total took none?

A.10 B.11 C.12 D.14 E.0

OA is A

Regards
MSD
When the going gets tough, the tough gets going.
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Source: — Problem Solving |

by dmateer25 » Sat Dec 06, 2008 5:59 am
I am coming up with B.

What is the source of this question?
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by vivek.kapoor83 » Sat Dec 06, 2008 6:20 am
True # of objects = (total # in group 1) + (total # in group 2) + (total # in group 3) + (total # in none of the groups) - (# in only groups 1&2) - (# in only groups 1&3) - (# in only groups 2&3) - 2(# in all 3 groups)


...is the formula

acc to ths
50 = 22+15+14 +x-9-2
50 = 51-11+x
50 -40 = x
x=10
IMO A.
Hope it helps.
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by dmateer25 » Sat Dec 06, 2008 6:21 am
vivek.kapoor83 wrote:True # of objects = (total # in group 1) + (total # in group 2) + (total # in group 3) + (total # in none of the groups) - (# in only groups 1&2) - (# in only groups 1&3) - (# in only groups 2&3) - 2(# in all 3 groups)


...is the formula

acc to ths
50 = 22+15+14 +x-9-2
50 = 51-11+x
50 -40 = x
x=10
IMO A.
Hope it helps.
Ah i multiplied by 3 not 2 for the 1 person in all three groups.

Thanks.
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by msd_2008 » Sat Dec 06, 2008 5:00 pm
How does this formula apply to AUBUC kind of set questions?
I always thought that the formula for AUBUC = A + B + C - AB - AC - BC + None - All .......note that we are not subtracting 2xAll in this formula.
Is this formula incorrect?

Regards
MSD
When the going gets tough, the tough gets going.
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by cramya » Sat Dec 06, 2008 5:31 pm
A good one!
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