Solution to Puzzle #99: World’s Most Famous Puzzle Currently

This was a relatively simple puzzle and I received many correct solutions to this puzzle. Ritesh, one of my colleagues, was the first one to respond in literally 30 seconds. Many others gave correct answers that include – Utkarsh (another office colleague), Anirudh Baddepudi, Bharat Kashyap, Prateek Poddar, PR Kumar and someone anonymous (through comments on the site). Well done everyone!

July 16 is the answer. I am taking the liberty of reproducing the answer from Anirudh Baddepudi:

After the first clue, we can rule out any birthdays in May or June as these have days which only appear once (numbers). Then there are 5 possible dates when the birthday could be.

After the second clue, we can rule out July 14 and August 14, because Bernard would not know which day is the birthday between these 2 if he was given 14. Then there can only be August 15, August 17 and July 16 left. However, if Albert knows the birthday in the last step he must have been given July has his month. This is because if he was given August he would have a choice between August 15 and August 17 and would not know when Cheryl’s birthday was.

Hence, we are left with July 16, which must be Cheryl’s birthday.

Prateek sent a link from New York Times that has a good solution to this puzzle as well:

http://www.nytimes.com/2015/04/15/science/answer-to-the-singapore-math-problem-cheryl-birthday.html

And he also shared a link that his friend sent, which is a more difficult version of the puzzle. The die hards may want to try this one out.

http://www.cseblog.com/2015/04/advanced-cheryls-birthday-puzzle.html

Hope you all enjoyed the puzzle.

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