What's 5 x 3?
Recently, the grading of this answer sheet went viral on the Net. The issue? For the question, what is “5 x 3”, the kid had solved it by calculating “5 + 5 + 5” but the teacher marked it Wrong indicating the correct way to solve it was by calculating “3 + 3 + 3 + 3 + 3”. What’s the difference, the Internet screamed. I agreed. In fact, I had written a blog on a similar topic a year back based on Richard Feynman’s comment in The Pleasure of Finding Things Out : “The whole idea was to find out what x was and it didn’t make any difference how you did it–there’s no such thing as, you know, you do it by arithmetic, you do it by algebra.” Of course, this being the Net, you can find a counter argument (if you choose to look). Sure enough, I found a good one by Brett Berry as to why the teacher may be right after all: “In the above problem 5 x 3 is equal to 5 + 5 + 5, but they’re not necessarily equivalent.” Huh? Another example from Berry makes the difference between...