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[obm-l] Numeros no chapéu
Olá pessoal !
There are 3 persons (let's call them A,B and C) in a room. Each of them wears a hat with a positive integer number marked on the hat. Each of the three persons can see the number on the two other hats, but cannot see the number on his/her own hat.
We tell them that one of the number is the sum of the two other numbers but they don't know which one is the sum of the two others.
We ask A: Do you know what is your number?
A looks at B and C, thinks and answers: I don't know.
Note here that the three persons are very intelligent and if they say that they don't know, it is because there are no possibility for them to deduce their number.
We then ask B: Do you know what is your number?
B looks at A and C, thinks and answers: I don't know.
We then ask C: Do you know what is your number?
C looks at A and B, thinks and answers: Idon't know.
A thinks a little and say suddenly:
Wait a minute! Now I know my number! I have 50.
What numbers have B and C respectively?
"Se enxerguei mais longe foi por estar sentado aos ombros de gigantes." (Isaac Newton)