Math Question Which Went Viral in The Social Media

Few days ago, there is a math question circulating in the online media. The question went viral, because rumour say that the question is meant for P5 student, yet many adult are unable to solve it correctly. Baby Shop SG understand that this has create some concern to the parents, whether their son/daughter are under tremendous stress at school, given such a tough question.

This headline also being picked up by overseas newspaper.

It was discovered later on that the question was meant for Sec 3 Math Olympic Question. The question and the answer are listed below.

THE SOLUTION

OUT of the 10 days, some numbers are repeated, only “18” and “19” are listed once.

If Cheryl’s birthday happened on either of these two days, then Bernard (who was given the day but not the month) would have known immediately when it was.

As Albert is sure that Bernard can’t possibly know the birthday yet, then her birthday cannot fall on the months where the “18” or “19” occur. So it can’t happen in May or June, and must fall in July or August.

With this new information, Bernard can now pin down Cheryl’s birthday for two reasons:

Two of the remaining five days are dated the 14th – as this number is repeated, it cannot be Bernard’s choice, and they can both be ruled out.

With three remaining dates – July 16, Aug 15 and Aug 17 left, Bernard knows the correct date.

By this time, Albert (who was given only the month) also knows the birthday.

As there are two dates in August, Albert would be sure of the date only if Cheryl’s birthday was in July.

Therefore, Cheryl’s birthday is on July 16.

Source: Singapore and Asian Schools Math Olympiad

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