triangle puzzle heres a puzzle my friend gave me, I can't crack it :( There is a logical reason for the numbers on each of the triangles but they do not form a series. Work out the ?           16           /\         /  \         / 6 \ 18  ------ 19           22           /\         /  \         / 1 \ 14  ------ 14           2           /\         /  \         /19\ 18  ------ 14         20           /\         /  \         / ? \ 11  ------ 25 Charles Taylor Friday, January 07, 2005 Well, This is just a wild guess, but maybe it's true. Since you said that by definition the numbers do not form any series, I tried to sum up all numbers in every triangle. I got: 59,51,53 and 56+? Thus my guess would be ?=1, since 59 - prime. 51 - not prime 53 - prime 57 - not prime All are in [50..60] range and odd numbers, as for even numbers the question of primarity wouldn't rise. Max Binshtok Friday, March 04, 2005 That's a good answer and I would certainly give you the credit but the answer is I am assured 6.  I have no idea why ;) This question came from a magazine and was 'Mensa' puzzle. Nice work. Charles Taylor Friday, April 01, 2005   Fog Creek Home