I am simply amazed how one single puzzle has proliferated across the social media in the last 10 days – the puzzle from Singapore, popularized by Alex Bellos’ blog in The Guardian. Many of you would have seen this, but I thought it is a nice puzzle, and hence putting it on the blog. This will be an interesting one to go through even with younger children.
Here is the puzzle:
Albert and Bernard Just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates:
May 15 May 16 May 19
June 17 June 18
July 14 July 16
August 14 August 15 August 17
Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively.
Albert: I don’t know when Cheryl’s birthday is, but I know that Bernard does not know too.
Bernard: At first I did not know when Cheryl’s birthday was, but now I know
Albert: Then I also know Cheryl’s birthday.
So when is Cheryl’s birthday?
As always, please send your answers directly to me at alokgoyal_2001@yahoo.com. If you like the puzzle, please share it with others. If you have interesting puzzles to share, please send them to me at my e-mail given above.
Happy birthday!
Alok Goyal's Puzzles Page 
Many of your puzzles are more difficult than this.. kind of surprised that this one is so written about 🙂
I agree, this is a simpler puzzle. Once anything catches life on social media, it can be a real hit.
I think its 15th aug.
Regards, Saurabh aggarwal
Sent from my iPhone
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As 18 and 19 are unique so they r cut out.. .with may and June months together Left days July and Aug… So if Bernard exactly knows date as he says “now I know d day” is July only as otherwise he would b confused between 15 and 16 Aug but he was not confused so its July 16
July 16th
First comment eliminates May and June
Second comment eliminates the 14th
Third comment eliminates August