Comment by wortiz | Hacker News Reader

Comment by wortiz | Hacker News Reader

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I'm going to chime in from experience and say that your college algebra students are the bottom of the barrel in regards to math students. With that respects there can be many reasons why they are there: they didn't care about math, they never really understood math, and/or they never really tried to get math.

If you are judging the ability of finishing word problems in the textbook, I'm assuming for homework assignments, and they really don't understand the actual math I think your problem is probably that most are using a solutions manual or spending what would seem too much time solving the homework problems.

As for solving word problems or practical problems I believe that this is exactly what math should be for especially at the college algebra level. To be serious most students entering college who want or are going to pursue a degree in mathematics are going to start off closer to the calculus level and maybe trigonometry depending on underlying circumstances. What people in college algebra are going for is a degree where math has to be practical and the more diverse applications they see the better. To give a simple example take logarithms: if you were to teach logarithms on the sole basis of algebraic symbols and expressions when it comes time that these students need to apply logarithms to real world problems (like say compound interest) there is going to be a good chance that they didn't really comprehend logs when they were taught them and won't be able to use them properly.

Which brings me to another point for word problems: word problems exist because they make students think and relate math to the real world it is fundamental to learning for many students to apply mathematical concepts in a multitude of ways in order to actual grasp a concept and one of the easiest ways to do this is to place that concept into word problems.

I strongly disagree with the notion that college algebra ought to be the place where one learns practical applications of mathematics. A valuable skill for any educated person is the ability to plod through minutia and make sense of it. Being able to be focused on the point at hand and not let distractions cloud judgment is a valuable skill.

If one really understands the mechanics of logs then I think they will not freak out when presented with a formula involving logs. I'm all in favor of applications but isn't this the job of other subjects? The applications should be taught in the subjects that apply it. The goal of a mathematics class ought to be to understand mathematics.

This lecture,

http://www.youtube.com/watch?v=WwslBPj8GgI

is long but well worth watching. He provides strong evidence that students learn to solve word problems but haven't the slightest idea of what is really going on. They are memorizing steps. This happens at Harvard and the community college.

I've given my students the standard word problems on travelling problems. They get the problems right. Then I ask them this simple problem and they universally get is wrong:

You drive 1 mile at 40 mph and then the next mile drive 60 mph. What is your average speed? (Almost everyone says 50 mph.) We aren't teaching thinking skills. We are teaching memorization of problem types. Almost none of them is actually practical, correct, or useful.

But why are we teaching travelling problems in a math class? I think it should be taught in physics.

To answer your last question first I think traveling problems are taught in math because speed and time are easy for students to relate to, the same way that finding the height of a flagpole by its shadow problems are easy for students to visualize and relate to. As for average speed that is one of those concepts that really isn't that relatable and should probably require an introduction beforehand.

As for the goal of a math class being that students should come out understanding math I completely agree but the beauty of math is that it is applicable everywhere and the goal of teaching a math class should be that students understand mathematics and where to apply it.

I couldn't imagine being taught vector calculus without some mention of applications and examples, my professor catered more towards mathematics majors with an abundance of Tensor notation and proofs but he never failed to understand that many in his class learned well by physical and other practical examples such as magnetism or fluids and so on.

Although I failed to watch your video I believe there is most likely a counterargument to word problems and what effect they have on students because if students really are solving word problems with the math they are learning the issue isn't that they don't understand what is going on but rather how to apply it to an actual math problem. Either that or the word problems do not incorporate well enough with the math that a student can grasp it quickly without knowing underlying ideas.

The experience of the professor at Harvard in the video contradicts your last paragraph. They know how to apply the math but they don't understand the problem. And the traveling problem I gave underscores this point. It's a very simple problem and almost no one gets it correct.

Then perhaps you and him are assigning the wrong word problems or not giving proper introductions to said word problems.

If all students are taught to do is "memorization of problem types" (to borrow GP's term), then they will only be able to handle actual problems that match one of the necessarily finite set of types of problems they have memorized. A different selection of problem types to memorize will not provide general coverage -- that requires learning to construct a solution to a new type of problem.

Nowhere in the thread has it been demonstrated that it would be impossible to design a word problem that does require the construction of a solution.

One of the problems I had with my dif. eq. class was that the grad student teaching the class just focused on "tank problems" and other "x problems" sets. So I see why story problems alone are not helpful. But, if they're judiciously used to encourage the understanding of abstract mathematical concepts, I think they are invaluable.

Perhaps you should watch the video and then you would realize that your characterization of this professor and me is wrong.

His argument is that current HS math doesn't provide enough distractions. Students don't learn to focus on the problem at hand, because the problem is already in sharp focus. All the variables are provided. The word problem is a slightly jumbled description of the formula to use. All you have to do is look up the formula, then plug in the variables.

Your students can't solve the travelling problem for the very reasons he's talking about. That problem is completely unlike anything they've ever solved in high school, because it doesn't give them the numbers to average. It's a two step problem where they need to use the given numbers in one formula, to get the resulting numbers for the second. HS students don't learn to solve problems: they learn to match paragraphs to formulas, then plug and chug.

Also, don't be such a purist. It's not useful. There is a great deal of overlap between math and physics. Physicists often invent new math to understand physics, and old math is often found to describe some newly discovered physical phenomenon.

You wrote:

"HS students don't learn to solve problems: they learn to match paragraphs to formulas, then plug and chug."

I agree completely and this is why I advocate for an end to the focus on so called practical word problems in high school in algebra classes. It should be in physics where one learns about travelling problems not in algebra. The focus on so called practical word problems is not accomplishing the goal and it's distracting from the learning of mathematics.

I taught physics in a community college as a full-time prof for 10 years, and had the occasion to teach math there a few times as well. After that stint, I started work with an ed software company developing math content for algebra students in the cc.

In my experience, the "word problems" can be used to motivate the students as to the interesting part of what they are studying. My focus wasn't on making them learn how to reason through complicated applications, it was on getting them to master the skills. So in that sense I agree with you. However, building a story around it (how do you determine which cell phone plan to buy?) helps keep their attention and shows them that they- yes THEY (the "bottom of the barrel" as was noted above- but I'll clarify this below)-- can apply math to their lives and live more intelligently. And getting students to that stage is my life's mission.

I think where math goes wrong is displayed beautifully in the rational expressions units (I didn't go to the original link, so forgive me if I'm entirely redundant here). When I was building the math content for the ed s/w company I was struck that nowhere in the chapter where students learn to simplify fractions involving a polynomial numerator and a polynomial denominator (tough stuff when you are first learning it) nowhere in the textbooks did they tell the student WHY. Why do all this hard work? What is the answer that we seek from all this?

[rant] About the idea of "stupid teachers teaching stupid students" in community college: Anyone who truly speaks from experience knows better. In a cosmopolitan setting you will have downright brilliant students in your classes- especially in your night classes. I've had many ivy-leaguers in my classes, top accountants for Exxon-Mobile and other high-power operators, sometimes from government agencies (I taught in Alexandria Virginia, about a mile from the Pentagon, where Mrs. Biden currently teaches). A common reason for them to be there? They've burned out in their careers and want to do something that "makes a difference." Going to med or vet school was common. They've got the degree, they've got the grades, they just need a couple of classes that they didn't take as undergrads, they're too smart to spend the money on a school that won't help them any more than a little ol' cc will. Keeping their job for an extra year and taking night classes is a smart move, so they come to the local cc. [/rant]

"I think where math goes wrong is displayed beautifully in the rational expressions units (I didn't go to the original link, so forgive me if I'm entirely redundant here). When I was building the math content for the ed s/w company I was struck that nowhere in the chapter where students learn to simplify fractions involving a polynomial numerator and a polynomial denominator (tough stuff when you are first learning it) nowhere in the textbooks did they tell the student WHY. Why do all this hard work? What is the answer that we seek from all this?"

What do you think are the answers to your questions?

One thing that was quite easy to do is to set the rational expression equal to something and solve for one of the variables. We did a lot of problems where there was only one variable: (x^2+9x+20)/(x^2-25)

In motivating them you don't necessarily have to give every reason to learn something, just reason enough to buy into what you are trying to teach them.

But the motivation for solving complicated rational equations does not come from word problems. The word problems for this topic involve very simple rational functions. My point has been that the motivation for studying and doing much of mathematics ought not come, solely, from practical word problems.

I agree with you that you (we) shouldn't feel the need to have a one-to-one mapping between problems we solve and word problems. Even in elementary physics you could argue that the word problems in many cases aren't practical, but we teach it to teach the flavor of the approach; the attitude of how we attack problems (or, less poetically, what exactly we mean when we say "cause and effect").

That said, the motivation is still greater when the students see some hope that what they are learning is meaningful.

What that motivation is depends on the level of the class. For algebra 2, it might be "we learn to manipulate rational functions because it gives us a tool to understand (or solve) a certain class of problems. Someday you may own a business where you have to worry about the average cost of something that depends on things that change alot, or variables as we call them. And you know what an average is: it's the amount of something divided by how many there are. Well if your amounts are represented by an algebraic expression, and your total is represented by an algebraic expression, then the quantity you will be interested in will look something like this (writes a rational function on the board). Now, what the fuck do we do with this?"

In response to yequalsx:

I see 2 applications of rational expressions off the top of my head: 1) From an abstract viewpoint, the message is "We can do the same stuff with polynomials that we do with integers. The only issue is that factoring is harder." This message gets very garbled 2) Solving ratio problems A/B = C/D come up very often. For example: I've won 43/87 freecell games. How many in a row do I have to win to get to 70%?

I agree with both of these examples. And here is my point. The sort of practical applications of rational functions involve very simple rational functions. So if our motivation comes solely from word problems then the natural question is why are we learning to manipulate

( x^2 + 2xy + y^2)/(x - y) + 1/(x^2 - y^2)

Has there ever occurred a practical application in which this expression has come up? If our motivation is expanding our understanding of manipulating algebraic objects then this expression is very much a practical application. It's an extension of an existing idea - rational numbers - to a new class of objects. Be able to do this sort of abstraction is useful in mathematics, and in fact is the essence of mathematical thought. It's also useful in things like programming.

The motivation for learning to manipulate rational expressions has to come well before you get to this.

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