If:

13 + 10 = 24 and
19 - 11 = 7 and
5 x 4 = 29 and
14 / 2 = 4

What is 23 / 5?

Let $ represent one of the arithmetic operators (+,-,x,/) and let $$ represent the variant "crazy" operator used in the puzzle. Then:

a $$ b = ((a+1) $ (b+1)) - 1

Test this theory:

13 + 10 => (13+1)+(10+1)- 1 = 14+11-1 = 24

19 - 11 => (19+1) - (11+1) - 1 = 20 -12 - 1 = 7

5 x 4 => (5+1) x (4+1) - 1 = 6x5 - 1 = 29

14  / 2 => (14+1)/(2+1) - 1 = 15/3 - 1 = 4

so all check. To determine, 23/5 is now easy:

23 / 5 = (23+1) / (5+1) - 1 = 24/6 - 1 = 3

3 is the answer.

Posted by Paul on 2008-10-10 21:50:29