puzzle (math, psychology)
posted by kayla .
You have 3 measuring spoons. Spoon A is filled with 8 tsps of salt. Spoon B and C are both empty; Spoon B can hold 5 tsps and Spoon C can hold 3 tsps. Divide the salt among the spoons so that spoon A and spoon B each have exactly 4 tsps of salt and spoon c is empty.

1) fill C from A  A=5, B=0, C=3
2) fill B from C  A=5, B=3, C=0
3) fill C from A  A=2, B=3, C=3
4) fill B from C  A=2, B=5, C=1
5) fill A from B  A=7, B=0, C=1
6) fill B from C  A=7, B=1, C=0
7) fill C from A  A=4, B=1, C=3
8) fill B from C  A=4, B=4, C=0
tada 
Wow, look at you go! How did you do that economyst?!

Its just logic. Plus it helps if you have seen the problem before.