Addition at five

My daughter, who’s five, has been learning addition of late. She knows a lot of the single-digit addition, like one plus two, three plus three, like that, but what’s funny is that instead of saying, “One plus two equals three,” she tends to say, “Plus one plus two equals three.” It’s that extra “plus” that prefaces the statement that totally makes me think she’s doing math via Polish notation.

I know, only a computer geek would get that.

0 = -1

Back when I was a freshman in high school, and had an inadequate grasp of higher mathematics, I came up with an algebraic “proof” that I thought violated, well, something in math. I had “proved” that 0 = -1 using infinity. It was pretty basic. I don’t know why I remembered this today, but I thought it would be amusing to post.

It’s like this:

The symbol ∞ represents, well, infinity. So, you whittle infinity down to a simple variable and start with:

∞ = ∞

Nothing earth-shaking. But infinity being infinity, you could also say that infinity minus one (∞ – 1) is also infinity, since it still goes on forever. Then you’d have:

∞ = ∞ – 1

Then, following the rules, drop out the variable ∞ from the equation by subtracting it from both sides of the equation:

∞ – ∞ = ∞ – ∞ – 1

Which of course leaves you with:

0 = -1

Proof! :)

Then, of course, you could further apply various equality rules and come up with all sorts of non-zero results equalling zero.

I remember being pretty disappointed when it turned out to be appallingly wrong. Fortunately, I still went on to the Advanced Math and then Calculus courses…

Silly math tricks

For some reason, these kind of math gimmicks always remind me of upside down calculator spelling. They’re amusing, but I really have to wonder who sits around and thinks these things up? Anyway, here’s what I just received via email from a friend (slightly edited):

“Chocolate mathematics”

1. First of all, pick the number of times a week that you would like to have chocolate. (Try for more than once but less than 10.)

2. Multiply this number by 2 (Just to be bold)

3. Add 5. (for Sunday)

4. Multiply it by 50.

5. If you have already had your birthday this year add 1754. If you haven’t, add 1753.

6. Now subtract the four digit year that you were born.

You should have a three digit number.

The first digit of this was your original number (i.e., how many times you want to have chocolate each week).

The next two numbers are:

Your age! (Oh yes, it is!!!!!)

This is the only year it will ever work, so spread it around while it lasts.

Incidentally, yes, it works.