Shared by Kenneth Kong, a Singapore TV host, this question apparently comes from a 5th grade-level math paper and is a somewhat infuriating logic puzzle.
Let’s analyze the statements and, by process of logical elimination, we can figure out the answer:
“I don’t know when your birthday is, but I know Bernard doesn’t know, either.” – Albert
Albert knows that if Cheryl had whispered to Bernard either “19” or “18” then Bernard would definitely know as there is only one date each for those numbers respectively (May 19 or June 18).
Therefore, if Albert’s first statement is true, Cheryl couldn’t have said to Bernard May or June either- thus eliminating half of the possibilities (we are left with July 14, July 16, August 14, August 15 and August 17)
We then go on to the second statement:
“I didn’t know originally, but now I do.” – Bernard
If Bernard now knows, we can be sure that Cheryl didn’t tell him “14” as there are still two options (July 14 and Aug 14). So we can eliminate those dates. That leaves us with three possible answers – July 16, August 15 and August 17.
Now the final statement:
“Well, now I know too!” – Albert
Using that same logic, for Albert to know as well the month must be July, as if Cheryl has told him August he would still have two options (August 15 and August 17).
Thus the answer is July 16.