Fog Creek Software
Discussion Board




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

*  Recent Topics

*  Fog Creek Home