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# The town rules in Kid-Town require each house to have

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Director
Joined: 08 Jul 2004
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The town rules in Kid-Town require each house to have [#permalink]  04 Aug 2004, 00:46
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Hi all
The town rules in Kid-Town require each house to have at least a ping-pong table or a soccer-table. If there are 50 houses in Kid-Town, how many houses carry both types of tables?

(1) The number of houses that have a ping-pong table only is 20.

(2) The number of houses that have a soccer table is 40.
Senior Manager
Affiliations: CFA Level 2
Joined: 05 May 2004
Posts: 267
Location: Hanoi
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I don't really understand this question.

A, B and D are clearly out. Consider C and E.

Take x as the number of houses which carry both types of tables.

From (1) we have: the number of houses with a ping-pong table = 20 + x
From (2) we have: the number of houses with a soccer table = 40 = x + the number of houses with a soccer table only.

From (1) and (2) we have: 20 + x + 40 - x = 50 unreasonable. Anyone can explain???
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CIO
Joined: 09 Mar 2003
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I have the same problem.

taking them together, I've built the venn diagram, and put an x in the center, a y in the "soccer table only" side, and 20 in the "ping pong only" side. That means that x+y must equal 40, and 20+x+y must equal 50.

That just doesn't compute.

I'm assuming that there are exactly 50 houses, and each one has at least one, since the law makes it clear that that must be so.

Surya_s, what did you mean by "read it carefully before you answer"?
Director
Joined: 08 Jul 2004
Posts: 604
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Hi Ian
This is courtsey of bluetooth
The problem here is that normally we take E when (1)+(2) --> NO UNIQUE RESULT but in this case, we take E when (1)+(2) --> UNREASONABLE.
So E is the right anwer, as you got.
CIO
Joined: 09 Mar 2003
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Kudos [?]: 34 [0], given: 0

where is this question from?

unreasonable isn't really an option. it likely wouldn't be that way on the real test.

You see, the data sufficiency questions always work out. It's not possible that the conditions in this town actually exist. On the data sufficiency, the question writer always starts with a real problem with a real answer and then takes information away, not the other way around.

If he's taken away too much information, and doesn't give enough back int he statements, then it's E. But he won't give back information that doesn't work out, because he won't change the information he started with.

That's why the two statements will never contradict each other, because they apply to that same question.

Does that make sense?
Director
Joined: 08 Jul 2004
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Hi Ian
What you are saying does make sense. I got this question from som ebody in the forum. so it might not be correct.
S
CIO
Joined: 09 Mar 2003
Posts: 464
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Kudos [?]: 34 [0], given: 0

Fair enough. Data sufficiencies are hard to wrap your head around. they have a lot of nuances that make them very difficult for many people. The less noise, the better, so I'm glad we had an opportunity to discuss one like this. Hopefully it will help people better understand ds as a whole.
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