I was tutoring the guy I do literacy tutoring for yesterday, and one of the problems was calculating the volume of a cylinder. Ok, fine I show him how to figure the area of a circle (pi r squared) and multiply it by the height. Done and done.

But then, I show him the answer in the back of the book to prove how smart I am, the answer was right but they used a different formula and they used diameter, not radius. And the multiplier, instead of pi, was .784 or something like that. So I told him to do it my way instead, but it irritates me that I can't figure out where that number comes from. Does anyone know?

lol @ "so i told him to do it my way instead"

when i used to help my little brother with his homework i'd come up against that all the time. i could get the right answer, but not the way he was supposed to.

fancy newfangled math.

sorry, dude i suck at math. i have no idea where any of those numbers come from.

what's a cylinder?

lol- me up there. force of habit.

Well I've been harping on him over Pi R Squared for like a year, and he still hasn't memorized it, so I'm not throwing another formula at him!

No one is good at math.

I am

HA!

i KNEW it!

I'm screwed.

The formula for calculating the volume of a cylinder using the diameter, instead of the radius is: (Pi x Diameter Squared x Height) all over 4. Using .784 is just a way to use multiplication instead of division, because when you divide Pi by 4, you get approximately .784. Make sense?

Yeah. I figured it was a fraction of Pi but I didn't know what. Why 4?

... because you are using twice the radius, times itself, which is 4?

Contrary to the implication that knowing 2 formulas for calculating the volume of cylinders makes me "good at math" I'm really not. I just know what I know. I'm moderately good at geometry and I guessed that your number was somehow a derivative of P1, so...

That's a long way of saying: I don't know But my guess is that if you play around with both formulas long enough, the answer will come to you.

What pisses me off is - this is a test for fricken waste water workers. These people shovel shit for a living. Now why on earth would you throw a whole new formula at someone who maybe or maybe not graduated high school? I've been trying to drill Pi into this dude's head for months. The people who write the practice exams for these are sofa king stupid. This isn't the first time I've looked at their math and said "why the hell did they do it that way?"

Well, my guess is, it's a publishing thing. There's millions to be made selling text books. And if the new version has the exact same formulas, how they gonna sell it? The fundamental math hasn't changed. They're trying to sell the idea that multiplying by .5 and dividing by 2 are two different animals, when they're really not. But again, it looks different and new, so it's an excuse to keep the machine going.

Oh, and that was a long way of saying that it's because the text book industry is corrupt.

I missed my opportunity to respond with "I've heard Steven Hawking is good at math."

David, you put the wit in nit-wit.


Or, took it out. One of those.

I'm not sure which one is correct but I love the metaphor.

And I love the difference in answers one can get when dividing by .784 as opposed to using the entire equation for pi.

You could be off enough that, when calculating the volume of a propane cylinders capacity, you blow up the entire fucking neighborhood. Ooooops!

I was a late learner of diplomacy.
Meaning I got most of the required 64 freaking credits, that the school I attended, for high school but not all and thusly the paper necessary to use to roll up and smoke my gym socks.

So, 28 years later, to get my GED, I got a GED for Dummies book.
And in it, there was one of those questions on the practice tests. I got it right.
THE BOOK HAD IT WRONG!
One of those blow up the neighborhood type wrong answers.
And I called them, the publishers of the .....for Dummies people, on it. Through their website.
They acknowledged in a return e-mail to me that it was indeed wrong and that they would have to correct it in the printings.



And I still hate algebra.
And really haven't used it. Except to get my GED.






From time to time, the usual moment seems terribly beautiful.

In real life, I assure you, there is no such thing as algebra.
Fran Lebowitz

I am

I actually use algebra frequently and I wish I new more.

I use it every time I go to the grocery store!

When you buy FOIL? Harrrr

I am horrible at math - practical application. Most writers, I have found, are the same way. I can even screw up with a calculator.

I did very well in math in school though. They even skipped me a grade in math (went from 6th grade math to 8th grade). I really struggled though missing the fundamentals of 7th grade math.

I still would have sucked at math in real life anyway.

My Uncle Johnny is a Math Professor and my Aunt Sheila is a Chemist. You gotta be good at math to do that stuff don't ya?

Ginny - I prefer your method of solving the problem. It just seems less complicated.


When I try to figure out the volume of a cylinder, I usually just determine how many cans of beer I can empty into the cylinder. Then I drink the beer from the cylinder to celebrate when I discover the answer.