infuriating question is a logical one involving figuring
out a birthday from a restricted quantity of knowledge.
It was first posed to baby college students within the Singapore and Asian
Colleges Math Olympiads (SASMO) however shortly unfold across the
web after TV presenter Kenneth Kong posted it on Fb.
The questions is as follows:
Albert and Bernard simply turned mates with Cheryl, and
they need to know when her birthday is. Cheryl offers them a
checklist of 10 doable dates.
Might 15, Might 16, Might 19
June 17, June 18
July 14, July 16
August 14, August 15, August 17
Cheryl then tells Albert and Bernard individually the month
and the day of her birthday respectively.
Albert: I don’t know when Cheryl’s birthday is, however I do know
that Bernard doesn’t know too.
Bernard: At first I don’t know when Cheryl’s birthday is,
however I do know now.
Albert: Then I additionally know when Cheryl’s birthday is.
So when is Cheryl’s birthday?
Kong’s Fb publish acquired over 5,000 shares and he was
contacted by the chief director of the SASMO who supplied
some background on the query.
It was the 24th of 25 questions and was designed to sift out
the higher college students from the weaker ones. But it surely’s clearly
stumped nearly all of the world’s adults as effectively.
Henry Ong, SASMO’s govt director, went on to say that he
was happy on the curiosity the query had generated on the
So, have you ever labored it out but?
If you wish to know the reply – scroll all the way down to beneath the
The intelligent varieties at Singapore’s Study Room unravelled the query and are in a position
to inform us when Cheryl’s birthday is.
First we have to determine if Albert is aware of the month or the
day. If he is aware of the day, then there is no such thing as a probability that Bernard
is aware of the birthday, so it have to be that Albert is aware of the month.
From the primary assertion, we all know that Albert is certain that
Bernard doesn’t know the birthday, so Might and June ought to be
dominated out (the day 19 solely seems in Might and the day 18 solely
seems in June). In different phrases, if Albert had Might or June,
then he can not make sure that Bernard doesn’t know, since Bernard
may have had 18 or 19.
Following that assertion, Bernard is aware of that Might and June are
Then, Bernard is ready to know which month it’s. So it have to be
both July 16, August 15 and August 17 (not 14th as then he
Since Albert subsequently may also be positive of the date, he should
understand it’s July. If it’s August, he can’t be certain as there’s
August 15 and 17.
So the reply is July 16.
Did you get the reply proper?
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