A logic question about "Cheryl's birthday" goes viral
The clues give just enough information to eliminate most possibilities
It spread after a Singapore television host posted it to Facebook
Are you smarter than a really smart Singapore high school student?
See if you can figure out Cheryl’s birthday, the Singapore logic problem that’s got the Internet twisted into knots. Some are even saying it’s the math equivalent of the “What color is the dress” debate.
The puzzling problem went viral after Singapore television host Kenneth Kong posted it to Facebook.
Cheryl’s birthday challenge was meant to test the better high-school students competing in the Singapore and Asian Schools Math Olympiad, held April 8.
Here it is: Cheryl has a birthday, and she doesn’t want to share it right away. (Otherwise, we have no challenge to solve.) So she gives her friends Albert and Bernard a list of 10 possible birthday dates: May 15, May 16, May 19, June 17, June 18, July 14, July 16, August 14, August 15 or August 17.
A brief conversation between Albert and Bernard – who we assume are not lying for the sake of this problem – gives the reader enough clues to eliminate nine of the 10 dates and discover Cheryl’s birthday.
That’s assuming you want to celebrate with Cheryl after she’s put you through all that trouble.
See our video below for the answer from Georgia Tech Mathematician Matt Baker. The New York Times and the Washington Post have also posted solutions to the problem, along with explanations.
Of course, the Internet has offered other solutions.