A math and logic riddle that was used in a competition for teens as a part of the Singapore and Asian Schools Math Olympiad has got the world stumped, teenagers and adults alike. This question was posted on Facebook by a TV show host from Singapore and has since made its rounds on the Internet. Here’s the riddle. Try and see if you can figure it out.
WTF Cheryl? Why you gotta be so tricky?
Here are a few of the guesses and responses online.
This Singapore math problem craze does nothing for our egos. Thankfully, we are musicians. http://t.co/AKlzcaH652— kingsley flood (@kingsleyflood) April 13, 2015
people are saying this question is difficult but isnt it quite obvious the answer is May 19...... pic.twitter.com/v8LPsRYOaJ— Mateen Firdaus (@matsfir) April 11, 2015
When you write it down its actually quite simple. The answer is June 17.— I BEAT BLOODBORNE (@DrShafbonculous) April 13, 2015
Have you figured it out yet? If you’d like the answer, here it is. But don’t scroll down if you don’t want spoilers!
The only unique days are 18 and 19. If Bernard were given these two numbers, he would immediately know what day Cheryl’s birthday is. So how is Albert so sure Bernard doesn’t have 18 or 19? He must not have May or June, so logically we can cross out all the days in May and June.
At this point Bernard declares he now knows the answer. He too must have figured out from Albert’s statement that May and June are not the right answers. If at this point he knows, we must eliminate the numbers he could have had that would not allow him to know given the information he knows.
Bernard knows it could be July or August. If he has 14, he doesn’t know if it’s July or August, so he must not have 14. He either has 15, 16 or 17.
Now, Albert says he knows the answer. From Bernard’s statement, Albert too must have deducted that Bernard doesn’t have 14. At this point, if Albert knows then it can’t be August because there are still two options left in August.
The answer is July 16.
And everyone hates Cheryl.
Read More: 5 Lessons About Humanity #TheDress Taught Us