This logic test developed by the Singapore and Asian Schools Math Olympiad has been making the rounds online lately. It's a bit of a brainteaser.
And the kicker? It's written for teenagers.
It's spawned a lot of debate over the answer.
Some even question if the answer is possible from the information.
Here's a hint: Cheryl's birthday is not August 17th.
According to the brains at Singaporean digital news agency Mothership:
"Out of the 10 dates, the day ranges from 14 to 19, with only 18 and 19 each occurring once. If the day of Cheryl's birthday is 18 or 19, then Bernard would have known when Cheryl's birthday is since Cheryl has told him the day of her birthday.
But why does Albert know that Bernard does not know?
If Cheryl has told Albert that her birth month is May or June, then it is possible that her birthday may be May 19 or June 18. This means that Bernard may know when Cheryl's birthday is. The fact that Albert knows that Bernard does not know means that Cheryl has told her birth month is either July or August."
"Initially, Bernard does not know when Cheryl's birthday is, but how did he know after Albert has first spoken? Out of the 5 remaining dates in July and August, the day ranges from 15 to 17, with only 14 occurring twice. If Cheryl has told Bernard the day of her birthday is 14, then Bernard would not have known. The fact that Bernard knows means the day of her birthday is not 14. So now we are left with 3 possible dates: July 16, August 15 and August 17."
"After Bernard has spoken, Albert now knows when Cheryl's birthday is. If Cheryl has told Albert her birth month is August, then Albert would not have known because there are two possible dates in August. Therefore, the correct answer is July 16."
Seriously, Cheryl, this is NOT how you get friends to come to your party.
Credit: Aunty Acid