TIFR CSE 2016 | Part A | Question: 1

Question

Suppose the following statements about three persons in a room are true.

Chandni, Sooraj and Tara are in a room. Nobody else is in the room. Chandni is looking at Sooraj. Sooraj is looking at Tara. Chandni is married. Tara is not married. A married person in the room is looking at an unmarried person.

Then, Which of the following is necessarily true?

• A. Sooraj is married
• B. Sooraj is unmarried
• C. The situation described is impossible
• D. There is insufficient information to conclude if Sooraj is married or unmarried
• E. None of the above

Comments

A married person is looking at an unmarried person means there must be at least one married person who is looking to some unmarried person.

A married person is looking at an unmarried person doesn't mean every married person is looking at an unmarried person.

A married person is looking at an unmarried person doesn't mean A married person can't look at an married person.

There is no condition on unmarried person. he may look to some married person or may not.

Answer 1

"A married person in the room is looking at an unmarried person" ---this is satisfied when Sooraj is made married

$\underset{married}{\text{Chandni}} \longrightarrow \underset{married}{\text{Sooraj}} \longrightarrow \underset{unmarried}{ \text{Tara}}$

"A married person in the room is looking at an unmarried person" ---this is satisfied when Sooraj is made unmarried

$\underset{married}{\text{Chandni}} \longrightarrow \underset{unmarried}{\text{Sooraj}} \longrightarrow \underset{unmarried}{ \text{Tara}}$

As both are possible we cannot finalize it to A or B --- we need extra information so answer should be D

Comments

i have edited , i think both choiceses fulfil

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How come B is true ? Didn't get that :o

Married persons looks unmarried person . Sooraj is looking at thara means he is defintely married ..

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Chandini is married and she can look at Sooraj who can be unmarried.

Answer 2

The correct answer should be C)..Let us see how ..

It is given that Chandni is married and Tara is not married..Further a married person looks at unmarried is also given..

Now given Chandni looks at Sooraj ==> Sooraj is unmarried is followed from this instance

Also Sooraj looks at Taara ..Now Taara is not married .Also it is given : A married person looks at unmarried . So Sooraj has to be married as follows from this instance..

So both of the above instances are contradictory..

Hence it is an impossible event..But it is so if we are given information about who the unmarried person can look to..

Thus the given piece of information is insufficient.

Hence D) should be the correct answer.. 

Comments

A married person looks at unmarried

It does not say that

An unmarried person does not look at married/unmarried

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Yes exactly I got the point now..Missed the point earlier..:)..

I have to be extra careful on inference based questions..

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Option D is correct as Saroj is married or unmarried can't be concluded.