3 ms·

This is correct. Although this is how we solve the problem, how did B know? that's where problems like these bug me.

• detcader 12y ago
  B knows because B had the information "16th", and "16th" is unique among the July and August dates.
  • cafard 12y ago
    Quite, but B could have easily known "15th" or "17th" for all that A knows in this particular part of the story.
    • rwbhn 12y ago
      Nope, A knows July from the beginning - which rules those out. We, the readers, don't know that until A's final stmt.