2 + 2 = 5

So, assume you were counting rocks. You have two stacks. You count how many each have, and each have two rocks. You combine them and count four rocks in the grand pile. Seems like 2 + 2 = 4, right?

Well, lets try something else. Assume you have two ropes. You tie two knots in each rope. You then combine them and count five knots. Therefore, 2 + 2 = 5.

(reposting from facebook so others can see. :) )