Cheryl's birthday riddle
Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates.
May 15, May 16, May 19
June 17, June 18
July 14, July 16
August 14, August 15, August 17
Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively.
Albert: I don't know when Cheryl's birthday is, but I know that Bernard does not know too.
Bernard: At first I don't know when Cheryl's birthday is, but I know now.
Albert: Then I also know when Cheryl's birthday is.
So when is Cheryl's birthday ?
I saw Cheryl's birthday riddle problem on Vulcan post.
This question went viral on whole social media in a matter of days.
It started with a posting on Facebook, by Kenneth Kong, a television host in Singapore.
This question was asked in Singapore and Asian maths Olympiad.
According to reports this interesting question is for 5 th class.
Can you solve this ?
Sol. Below
Line 1:
Albert: I don't know when Cheryl's birthday is, but I know that Bernard does not know too.
Well Albert was given only month how come he know the date from 14,15,16,17,18,19.
But if we assume that dates told to Bernard is 18 & 19 then Bernard 100% knows the date &month . As these dates were only once in the list - May 19 & June 18.
This is also not possible .
As in the next line Albert confidently says Bernard does not know, that means he was told the months July & August.
Line 2:
Bernard: At first I don't know when Cheryl's birthday is, but I know now.
If the date is 14 then Bernard can't know Cheryl's birthday the both months have 14 date i.e.
July 14 & August 14 .
14 date - [removed]
If he knows full date then he must have been told 15,16,17 as these dates were occuring once in the list
August 15, August 17,July 16.
Line 3:
Albert:Then I also know when Cheryl's birthday is.
Here Albert said that he also knows the date , for him to know from the list
August 15, August 17 ,July 16
He must have been told month July as if he was told August he would have two possibilities: August 15 & August 17.
Ans: July 16
Cheryl's birthday riddle answer 👆
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