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Brain Teasers

by gmat740 » Thu Mar 05, 2009 1:23 pm
Question:1

Six persons- A,B,C,D,E and F sit around a circular table.Is the person opposite to D adjacent to the person Opposite to F?

1.) B is towards the right of D and F is to the left of E.

2.) F is in Between C and A.

Answer with Proper explanations
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Question 2

by gmat740 » Thu Mar 05, 2009 1:30 pm
Question 2.




The students of a class are standing in a row all facing North.How many students are between Adam and Bryan?

1.) The number of students towards the left of Adam is 15 and Bryan is 10th from the right end.

2.) One third of the total number of students are in between Adam and Bryan.

Answer with proper Question Number and explanations.
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by cramya » Thu Mar 05, 2009 6:15 pm
Q 2.

Stmt I

The number of students towards the left of Adam is 15 and Bryan is 10th from the right end

15 BRYAN ADAM 9 - >one possible combination (0 people between)

6 brian 8 adam -> 8 people

INSUFF

Stmt II

One third of the total number of students are in between Adam and Bryan

No idea on what the total number of students are

Together:


total = 18

8 BRIAN 6 ADAM 2

C

Hope I am not missing something or another combination/total
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by pakaskwa » Thu Mar 05, 2009 7:11 pm
Answer is E.

For me the only way to solve it is to draw out the possibilities. And it's time consuming. If anybody knows a better way, please share.

Draw a circle as the table. Clockwise mark 1,2,3,4,5,6 evenly spaced spots, as the seats for 6 people.

From the question stem, we know that if we want to meet the requirements, D and F must be adjacent. (Their sequence doesn't matter for now). I put D at seat 1. So F must be at seat 2 or 6.

On the other hand, if we place F at 3, 4 or 5, and still meet conditions in stmt 1 or 2, it means it's insufficient.

Stmt 1
I put F on seat 5, B on seat 6 (toward right of D), E on seat 4 (so F is on its left). This arrangement meets condition in stmt 1, but not the condition in question stem. Insufficient.

Stmt 2
I put F on seat 4, B on seat 6, E on seat 2. C and A are on seat 3 and 5. Now this arrangement meets conditions both in stmt 2 and stmt 1. But it still doesn't meet question stem condition. Insufficient.

Answer is E.
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by quocbao » Thu Mar 05, 2009 8:30 pm
Six persons- A,B,C,D,E and F sit around a circular table.Is the person opposite to D adjacent to the person Opposite to F?

1.) B is towards the right of D and F is to the left of E.

2.) F is in Between C and A.
---

I think the answer is C

From Stmt I, we know that B sit towards the right of D, and F is to the left of E. But we don't know whether F sit near D or opposite to B ( it can't sit near B because to the left of F is E ) => INSUFF

From Stmt II, we know that F between C & A, but we don't know about others. It could be ... C F A ... or .... A ? F ? C .... so we can't answer the question

Combine I & II

now we know that F can't sit near D or B, near D or B must be ether C or A. And we know that on the right of F is two persons: E and C or A. We wil have something like this

= D = B =
A = = = C
= F = E =

So D is actually opposite to F, and we can say no to the question.

That's why I choose C.

Just my 2c :-P
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by pakaskwa » Thu Mar 05, 2009 9:58 pm
Hi quocbao,

For this arrangement (thanks for the drawing example):
=B==D=
A=====E
=F==C=

- B towards the right of D
- F to the left of E
- F is between C and A
So it meets stmt 1 AND 2

However, the person opposite to D is F, so it's not adjacent to the person opposite to F (which is D). Sufficient to say NO.

So C is correct.
Last edited by pakaskwa on Fri Mar 06, 2009 4:35 am, edited 1 time in total.
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by hungryhippo » Fri Mar 06, 2009 1:37 am
Is this a question where "no" would be sufficient to answer the question?

pakaskwa proved that D needs to be adjacent to F for the statement to hold true and then in statement I and II it seems like it satisfies the condition that D cannot be adjacent to F.

so i would guess D as my answer?

unless "towards the right" and "to the left" do not mean that they are directly adjacent? is there an official ans out there?
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by pakaskwa » Fri Mar 06, 2009 4:34 am
Hey hungryhippo and quocbao, I think you guys are correct. C is the answer. I was not thinking straight. I'll remove my posting..
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Answers

by gmat740 » Fri Mar 06, 2009 7:28 am
Q2.


Q 2.

Stmt I

The number of students towards the left of Adam is 15 and Bryan is 10th from the right end

15 BRYAN ADAM 9 - >one possible combination (0 people between)

6 brian 8 adam -> 8 people

INSUFF

Stmt II

One third of the total number of students are in between Adam and Bryan

No idea on what the total number of students are

Together:


total = 18

8 BRIAN 6 ADAM 2

C



The answer is E
Please check again.
I will post the answer once you have taken another shot of this
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by Ramp » Wed Mar 11, 2009 12:43 am
yep answer to q2 should be E since combining two statements gives two different results.
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