When is Cheryl’s Birthday?
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 16 19
June 17 18
July 14 16
August 14 15 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 didn’t know when Cheryl’s birthday is, but I know now.
Albert: Then I also know when Cheryl’s birthday is.
When is Cheryl’s birthday?
Cheryl’s birthday is on July 16
From the first statement, any of the day’s in that month should not be unique, else otherwise Albert can’t be sure of Bernard not knowing the birthday.Lets take the possible answers
If it was May => Albert cant say the first statement, as if the day was 19, Bernard will know the birthday for sure.
If, it is was June => Same is the case with 18th.
If, it is in July => Albert can say the first statement.
If it is in August => Albert can say the first statement.
Now after hearing first statement, Bernard can clearly figure out that the month of birthday is either July or August.
So, if the day was 14 => It can be July 14 or August 14 =>as bernard know now, it is not possible
If the day was 15 => It can be Aug 15
If the day was 16 => it can be July 16
If the day was 17 => it can be Aug 17
Only three days possible are Aug 15, July 16 or Aug 17, bernard knows the day so he know the birthday.
From the third statement, Albert knows the birthday as well, so it can only be July 16, as if the month was Aug, Albert can not figure it out.
Thus the Cheryl’s birthday is on July 16.
Your Answer
More puzzles to try-
Dice Game with Math
On rolling two dices (six-sided normal dice) together, what is the probability that the first one comes up with a ...Read More »Can you cut and reassemble a square so that you create a red cross of the same volume?
Can you cut and reassemble a square so that you create a red cross of the same volume?Read More »A game of 2014 cards
There is a table with a row of 2014 cards. Each card has a red side and a blue side. ...Read More »Millionaire Puzzle
Solve the rebus riddle in the picture below.Read More »Friends coming over to you for water puzzle
You have a large number of friends coming over and they all get thirsty. Your first friend asks for 1/2 ...Read More »3 Switches and Light bulb Puzzle
There are 3 standard on/off switches outside a room. One (and only one) controls a light bulb inside the room ...Read More »Magic of Maths
Find out a multi-digit number that if multiplied by the number 9 or any of its multiplications products (i.e. 18, ...Read More »Clock Needles Overlapping
I have a clock(12-hour format) and both the needles of the clock overlap at 12:00. After how much time, they ...Read More »What is the current Temperature of London
This Rebus represents the current Temperature of London 0 ____________ B.Tech M.B.B.S What is the current Temperature of London? Read More »Arrange the Puppets
Sweet & very intelligent katty has 8 puppets(Jane Bird Barbie Angel Colleen Nora Lass Missy). All puppets are of different ...Read More »Tree that all carry in hand riddle
What is the tree that we all carry in our hand?Read More »Calculate Pay
A temporary employee needs to be paid everyday but the employer has only one rod of 7 units of gold. ...Read More »Age detrmination riddle
I was was with my friend one evening at his home, he had three daughters. I asked him how old ...Read More »You do everyday
Spelled forwards it is what you do everyday, Spelled backwards it is something you hate. What is it?Read More »Three Chinaman face black painted puzzle
There are three Chinese guys sleeping in a hotel room. Someone paints their faces with black color during the night. ...Read More »What is it that no man wants
What is it that no man wants, but no man wants to lose?Read More »Who Walks on Three Legs?
What animal walks on four legs in the morning, two legs during the day, and three legs in the evening? ...Read More »How Tom can do so?
Tom claims to do the following activity. 1. He puts a coin in a glass bottle. Then, 2. He shuts ...Read More »Ends that begins
It has a beginning, but no end, But it ends all things that begin. What is it ?Read More »Excuse me everyone, Please find the meaning of this riddle
Can you find out the meaning of this riddle? ABCDEFGHIJKLMNOPQRSTUVWYZ QQQQQQQQQQQQQQQQQQQQQQQQQRead More »