27 February 2014

New Puzzle

Thursday evening. No flight today. I got done with it on Monday. But still there is a puzzle…

Mary would like to go out with John but John did not care much for Mary. So Mary agreed to play a guessing game with him. John asked her to guess the apartment number that he first lived in. He let her know it was between 8 and 100 (both inclusive). But she had to guess with as few questions as she could.
Her first question was “Was the number more than 50”?
John answered the question. But what Mary did not know is that he lied. (he really did not care to go out with her).
Mary then asked “Is the number divisible by 4?”
John answered that question. But once again, he lied.
Mary thought for a while and asked “Was it a square number”?
This time John answered the question truthfully.
Mary excitedly asked her final question “I know the exact answer if you tell me if the number started with 3 or not”
John answered that question too. But we do not know whether he was telling the truth or not.
At that point, Mary proceeded to guess the apartment number. As you can imagine, she got it wrong. (After all John lied at least twice).
Now, can you tell me what was John’s apartment number?

Posted February 27, 2014 by Rajib Roy in category "Puzzles


  1. By Ramesh Krishnan on

    Yep 81 it is…. the only way Mary could have arrived at the answer was if john said (No, Yes,Yes).. which means the actual answers were (Yes,No,Yes) and the only number that fits with that is 81

  2. By Dhananjay Nene on

    Next time John asks some lady for her phone number, she should respond back with a challenge for him to guess it 🙂

    And yes Babs is right – has to be 81

  3. By Rajib Roy on

    Looks like quite a few people got the answer right. I assume then, I do not have to send the solution. Here are some that I saw the correct answers from: Debatri Chakraborty, Bijetri Chakraborty, Roy K. Cherian, Amlan Sen, Arka Ganguly, Subramanian Subramanian, Arnab Dey, Matt Tebbe, Devashish Chintamani, Chris Kramer, Balaji Kakkadasam, Hiten Chadha, Marek Cyzio, Sridhar Ramachandran, Dhananjay Nene, Ramesh Krishnan, and Russell Shaw. The answer is 81. Rupa Bamba, did you get to 81?

  4. By Dhananjay Nene on

    Heh, Rupa is far ahead of us in solving puzzles – instead of the silly ones like what is my apartment number she went for the big one like what is the ultimate question of life, the Universe, and everything 🙂


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