Wait! Here is the question!
Possible months are May, June, July & August & possible dates are 14,15,16,17,18,
19.
Days 18 & 19 appears only once in the list. If Cheryl had told Bernard any of these
numbers then he would have came to know her exact birthday straightaway. That
would also make first part of Bernard's statement (At first I don't know when
Cheryl's birthday is) false. So May 19 & June 18 eliminated right away.
Had Cheryl told Albert month May or June then his statement would have been like -
Albert - 'I don't know whether Bernard knows or doesn't know when Cheryl's birthday.
He might know her birthday if Cheryl have told him number 18 or 19.
Or he may be unaware of exact date if Cheryl have told him numbers 15,16 or 17'.
So with months May & June, Albert is not sure whether Bernard know or doesn't know
exact date. But here Albert assured with that the Bernard too doesn't know exact date.
Hence these two months also eliminated.
As Albert is saying Bernard too doesn't know exact date, he is indirectly suggesting
Bernard that month is not May or June.
From rest of list, number 14 appears twice - once with July & once with August.
Now from Bernard's statement he knows the exact date now.
If it was 14, then Bernard would have been uncertain with exact month(whether it is
July or August. So Cheryl must have told him number 15,16 or 17.
Now what Albert is saying in his next statement is that now he too know exact date.
If Cheryl had told month August then Albert wouldn't have an idea of exact date as
August has two possibilities i.e. August 15 or August 17.
Only date left is JULY 16 & That is Cheryl's birthday !
Note - For the logic behind the answer, thanks to Wikipedia.For simplification say
thanks to person named below!
