Stephen Yeung:       Arthur and Henry just met Michelle. “When’s your birthday?” Arthur asked Michelle.

Michelle thought a second and said, “I’m not going to tell you, but I’ll give you some clues.” She wrote down a list of 10 dates:

May 15, May 16, May 19

June 17, June 18

July 14, July 16

August 14, August 15, August 17

“My birthday is one of these,” she said.

Then Michelle whispered in Arthur’s ear the month — and only the month — of her birthday. To Henry, she whispered the day, and only the day.

“Can you figure it out now?” she asked Arthur.

Arthur: I don’t know when your birthday is, but I know Henry doesn’t know, either.

Henry: I didn’t know originally, but now I do.

Arthur: Well, now I know, too!

When is Michelle’s birthday?

Bob Choi:                June 18^th? On second thought... I dont know!

Metis Hon:               Michelle's other name is Cheryl. The problem is set by Henry Ong of the Singapore & Asian Schools Maths Olympiad to stretch the analytical skills of 15 years old Singaporean.

The answer is July 16. Don't ask me why, just look it up on Google.

I'm glad my sons didn't go to school in Singapore!

Tim Fook:                I have read from Newspaper about this so called “ mathematical question” issued in Singapore and I know the answer.

The logic of taking out the incorrect answer is how to single out the month and day separately from the dialogue. As a poor in Math. Like me, I just don’t quite understand the analysis.

As what Metis said, look for details in Google.

Metis Hon:               This is so easy, May 19 of course.