Jumat, 27 Maret 2009

Elementary math & reasoning skills

Someone recently sent me a VERY interesting link:
The Story of an Experiment

Photo by foundphotoslj

This experiment in math teaching was done in the 1930s by by L. P. Benezet, and the main gist of it was that formal arithmetic studies were delayed until the latter half of 6th grade. Instead, the instruction concentrated on "teaching the children to read, to reason, and to recite - my new Three R's."

They also were taught about numbers they encountered in their reading materials, about time, about measuring units, estimation, and coins. Finally in 5th and 6th grade they also learn skip-counting. Formal arithmetic, meaning paper-and pencil work with addition, subtraction, multiplication, and division using a textbook began in latter half of 6th grade and continued till 8th grade.

The experiment was a huge success. Mr. Benezet compared the children's abilities in the experimental classroom to those of the traditional classrooms, and every time the "experimental" children were able to reason out word problems correctly, whereas those taught traditionally just stumbled all around, trying to find some formula to use.

Maria's comments

I find this story very interesting and I've read it before. I can't say that approach wouldn't work better than "traditional math" even in today's world. Maybe it would! Those kids were taught to reason AND they were also taught some basic math skills, just without the use of mechanical formulas. So, they learned to think and reason it in their heads.

My guess is that such an approach would be even better if it was accompanied with some, what you might call, formal, instruction in math, BUT very much avoiding the idea that you use some formula that the teacher gives you "on a platter".

For example, in the experiment the kids were supposed to learn the numbers they saw in books and learn the page numbers such as 76 and 293. But, I wonder if this would have resulted in quicker/better understanding of number system had they been taught explicitly about hundreds, tens, and ones (the place value). Then again, we don't know how exactly the teachers explained those- maybe they did explain them in a very good way.

One of my instructors in university often mentioned the idea of school math being "announcement math" or "announced math". It's announced from a higher authority, without giving kids much in the way of justification, or the opportunity to find the truths themselves and thereby understand them deeper.

I do try to avoid that in the elementary part of math. In fraction studies, I refrain from giving "formulas" for fraction addition or division or simplification until kids have had a lot of experience with "doing" it with the fraction pictures. And even then the formula can be like a "sideline" that is mentioned in passing. I don't want to even deal with LCMs and GCFs when it comes to fraction math in elementary grades.

In general I always try to justify the math and let children experience and understand it on a conceptual level.

As regards to the experiment, they wanted kids to learn reasoning by the usage of good books and reading a lot. Then, when their brains were trained to a certain point, arithmetic was studied from books.

Reading a lot of books and learning reasoning is definitely a good way to go. But, I feel that mathematics, when taught right, can also have a part in this "training the mind" process and learning reasoning. It is very well suited to that if it is taught well during the elementary years - having the emphasis on thinking skills and concepts, not just memorizing formulas.

Rabu, 25 Maret 2009

The Best and Worst Jobs

You might find this interesting: in a study ranking the best and worst occupations in the US, guess where mathematicians landed!

#1.

The study was looking at job hazards, pay, stress levels, environment, and a few other factors. Take a look at it here: Doing the Math to Find the Good Jobs.

Now, this study didn't take into account an individual's likes and preferences and feelings ... If someone REALLY loves cutting timber in a forest, then obviously that's a perfect job for them. But it's still interesting to note that mathematician, statistician, biologist, software engineer, and other "thinking" jobs ranked very high.

Sabtu, 21 Maret 2009

Division of fractions conceptually

I've managed to make another video on a very important topic (I feel) of fraction division. I apologize for the audio; I do want to improve and we will definitely work on that to get it better next time.


Division of Fractions Taught Conceptually, part 1


Division of Fractions Taught Conceptually, part 2

The two parts of the video show a step-by-step approach for teaching division of fractions conceptually:

  1. Start with sharing divisions that divide evenly. For example, 4/7 ÷ 2 can be thought of as "Two people share 4/7 of a pie evenly. How much of the pie does each person get?"

    Children can figure these out mentally without using any rule.


  2. Continue to measurement divisions where we think, "How many times does the divisor fit into the dividend?". Again, the problems should first be designed so that the divisions are even. For example, 4 ÷ (1/2) means "How many times does 1/2 fit into 4?" Or, 3 1/5 ÷ 2/5 means "How many times does 2/5 fit into 3 1/5?" Again, no rule is necessary to solve these - just logical thinking.


  3. Next, study measurement divisions with the dividend of one. This leads to the concept of reciprocal numbers. For example, 1 ÷ 3/4 is thought of as "How many times does 3/4 fit into 1?" As I show in the video, and you should show visually, 3/4 fits into 3/4 once, and into the leftover piece of 1/4 it fits 1/3 of the way. So, all total 3/4 fits into 1 exactly 1 1/3 times.

    Students should do a sufficient number of these kinds of problems so that they get familiar with the thinking process. After that, take some of the problems they have solved, and write the answers as fractions instead of mixed numbers. For example we found above that 1 ÷ 3/4 = 1 1/3. Write 1 1/3 as a fraction, and you get 1 ÷ 3/4 = 4/3. Now, 3/4 and 4/3 are reciprocal numbers. If you multiply them, you get 1. And this happens with every such division problem.


  4. Lastly, we apply this neat pattern with reciprocal numbers to arbitrary fraction division problems, and thus arrive at the shortcut for fraction division.

    For example, 7 ÷ (4/5). Use the helping problem of 1 ÷ (4/5) = 5/4. Since 4/5 fits into 1 exactly 5/4 times, it fits into 7 exactly seven times that many times, or 7 × 5/4 = 8 3/4 times. Similarly, let's consider 6/7 ÷ (3/4). First look at the helping problem 1 ÷ (3/4) = 4/3. Since 3/4 fits into 1 exactly 4/3 times, it fits into 6/7 exactly 6/7 that many times. The answer is therefore 6/7 × 4/3 = 24/21 = 1 1/7.

    We can notice that for any fraction division problem, we end up multiplying the dividend by the reciprocal of the divisor! Students can actually notice and understand this shortcut on their own, using this method. It is no longer just a rule handed to them on a platter as, "Swallow this, no questions." It becomes a concept they can understand.


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