Gifted Issues Discussion homepage Forums General Discussion The Ultimate Bad Homework Question Thread!

Actually I missed the "about" before the "8." I only saw the second "about." (Ha! I fail the careful-reading test!) But I still think the significant digits analysis is too precise for the word "about." "About 8" could mean "somewhere between 7 and 9." Or it could mean "somewhere between 7.99 and 8.01." It all depends on your definition of "about." I still think the most correct answer is to do the exact calculation -- this is your least biased estimate of the real (unknown) value.

The mathematically correct answer (admittedly a bit absurd on its face) is to use one significant digit and round accordingly; I'm quite sure of this. But I also think that the correct 50,000 answer and the discussion we're all having here is math's way of saying, "You shouldn't do this calculation with only 1 significant figure. Go back and get another one to tack onto that 8, and then your answer will start making sense."

I suspect that the people who wrote the problem didn't have the slightest clue about what they were doing. And of course, with so many problems as bad as this one floating around, it's no wonder that so many American kids bomb out when they get to algebra.

I've read some reasonable-sounding criticisms of AP Physics; here's one on a blog called Quantum Progress.

From what I've read, people are questioning the content of AP classes. Many criticisms center on the idea that many or most AP classes are too superficial. This was certainly the case with the AP history class my son enrolled in and then dropped. It raced through almost 400 years of American history in 29 weeks. My understanding is that all AP US history courses cover this much material (some better than others). AP Physics (especially AP Physics B) has had some heavy criticisms in that regard.

As a counterpoint, I have an IB Physics textbook (author: Tsokos). It's 800 pages long and covers 8 main topics in 470 pages and some optional topics in the remaining pages. I've been surprised at the depth the book goes into. There's some really good stuff there. This is due, I think, to the fact that the course is designed to be taught over two years, rather than one.

Oh, the College Board has finally reformed AP Physics B, but the new classes won't start until 2014.

Yup. She's using Giancoli's Physics. Which is larded up with math-math-math and example-example-example, but is VERY light on conceptual instruction. Ergo, the expectation that students can examine 20 worked examples of quite specific problem-solving using Newton's laws of motion, have a single hour of direct instruction...

and then tackle several synthesis problems --without using any notes or calculator-- that also throw in unusual units and forces them to derive conversion factors on the EXAM...

would be... oh, what's the word? Laughable? No, diabolical, I think.

It's good to hear that it isn't just us. Personally, I think that what I've seen of the AP coursework so far supports the notion that these classes were "too hard" and so now they've gone the route of substituting quality for quantity (more! more! more!) in the same sleight of hand that has been featured in things like Race to Nowhere.

It's maddening. We didn't cover some of this stuff in my year-long COLLEGE course. No, instead we covered about 2/3rds of this-- but in considerably more detail. In that course, some of these questions would have been fair. Of course, I don't recall being asked to do what my high schooler is being asked to do until...


well, my qualifying exams in analytical chemistry as a graduate student, quite frankly.

That's how crazily out of whack the assessments are seeming.

This is a known problem in physics. Students can crank through problems and yet largely fail to understand concepts. Have you every heard of Force Concept Inventory? It's a wonderful tool for assessing conceptual understanding of forces in Physics.


I seriously do NOT understand this approach. I started to write "What were they thinking?" but I suspect that the answer is "They probably weren't." Or maybe it's that whole "make-merit-through-overwork" idea.

Well, you're right about how to calculate significant figures. But the idea of significant figures itself is merely a notational convention, not a mathematical truth.

Think about it: for a number like 5,000 to always be "more correct" under conditions of uncertainty than, say, 5,136 -- purely in virtue of its having all those zeros -- would have to mean that there was something magical about numbers that happen to end in zeros in base-10 notation.

The purpose of using numbers with all those zeros is merely to signal to others something about the precision of the estimate. It does not make the number a better estimate. It does not make the answer more correct.

But the fact that we can get into a friendly argument about this at such a high level of abstraction just shows how pedagogically absurd the question is for that age-group!

Yes, exactly!

That's the way I read it. In week one he jogs 2 miles/day, in week 2 he jogs 3.5 miles/day, in week 3 he jogs 5 miles/day, etc, and the question is in which week he'll reach 8 miles/day.

So I'd write out the initial expression as 2 + 1.5(x - 1) = y, and solve from there.

If atmospheric pressure CHANGES, then what happens to the absolute pressure at the bottom of a pool?

a) it is unchanged
b) it increases, but by a smaller amount
c) it increases by the same amount
d) it increases by a larger amount


:thud-thud-thud:

DD had to call the teacher about this one.

"Pretty sure that Pascal's Principle is what they're asking about here... but... uhhhhhh... I just don't think that DECREASES in atmospheric pressure are going to result in increases in pressure at any depth within the fluid."

Because if you plug in your values, when x = 1, y = 3.5. The extra 1.5 miles doesn't get added until week 2.