7 February 2014

Hourglass puzzle

Here is a puzzle for this week. You have two hourglasses – one measures 11 minutes and the other measures 13 minutes. But you need to boil some eggs for exactly 15 minutes.

How can you do that?

Remember: If you are seeing this on FB, message me the answers..

Posted February 7, 2014 by Rajib Roy in category "Puzzles


  1. By Kihtrak Srin on

    srini …comment and a question …comment – that is why Rajib has given you 2 hour glasses none of which measures an hour (sory, super kadi for your kadi :-)). Question – long time, how are you doing?

  2. By Rajib Roy on

    Answer to the puzzle: First and foremost, more than a dozen of my friends have accused me of lowering my standards in puzzles. I am absolutely disappointed that my friends still accuse me of having any standards whatsoever 🙂
    There are two prevalent answers I got – one requiring total of 26 minutes and another exactly 15 minutes (there was one variant given which required 37 minutes). The 15 minute version is the following: Start the 11 min and 13 min hourglass together. When the 11 min one is done, turn it. Let the 13 min one continue. Now at 13th minute the second one is done but the 11 min one has only 2 minutes (13-11) worth of sand fallen in. So just turn that upside down again. You will get 2 more minutes after the 13th minute giving you 15 minutes.
    A lot of people got the right answer – I am not publishing all the names this time…


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.