3 ms·

Others have described the solution in this thread, but I thought I would express it more visually since I still see some confusion: https://docs.google.com/pre

• swavaldez 12y ago
  I'm still confused by this "If Albert can tell from just the month that Bernard does not know, then we can rule out all of May and June"
  • rictic 12y ago
    Imagine you're Bernard and you've just been handed the day of the month. If you got 14, 15, 16, or 17 then you don't know the month, but if you got 18 or 19 then you know that the month is May/June.
  • ironrabbit 12y ago
    I shouldn't have tried to fit that on one slide :) Consider the case if the birthday is May 19th: - Bernard knows the date, and he knows that May 19th is the only possible "19th", so he knows the answer immediately. - Albert would know it's in May, and that May 19th is possible. So, he knows there's a chance that Bernard knows the birthday immediately. Since in the question, Albert is confident that Bernard doesn't know the birthday immediately, we can conclude that the month cannot be May. The exact same logic applies for June and the 18th. The only possible months are July and August, because every possible date in July and August also appears in another month. Hope that makes more sense!
  • deleted 12y ago
    [deleted]