General Chat

You are sitting at a table opposite a man at a fairground. There are three cups on a table. Two cups contain share certificates for one Microsoft share. One cup contains a cheque for £1m. You make a choice and choose one cup (without looking underneath it). After you make your choice, the person opposite (who knows what is under each cup) lifts one of the cups you didn't choose to reveal a Microsoft share certificate. You then have the choice of swapping cups (changing the one you chose for the other cup, still without knowing what is under each cup) and taking the prize of your final choosing. Assuming you want the £1m, should you swap cups and why?

Hiya Greg, Stick with my firsy choice, otherwise all I`m doing is doubting myself. Once I`ve made a decision,that`s it. Baz

You should swap. When you make the first guess as to where the cheque is, your chance of getting it is 1/3, and your chance getting a share certificate is 2/3. When you are presented with the chance to swap, you are reversing the odds, so your chance of getting the cheque becomes 2/3, and the chance of a share certificate becomes 1/3. In otherwords, when you swap, if you have the cheque you will get the share certificate. If you had the certificate, you would get the cheque. You were statistically more likely to ge the share certificate so if you swap, you are more likely to get the cheque.

Greg this was in the book 'A curious incident' apparently mathmatically you should change your mind!! not that I understood why!! :O)