MGTutoring.com. A Rational Perspective on Education.

December 3, 2012

Teaching Exponents

Filed under: Education,Gold Academy,Homeschooling,Logic,Mathematics,MGTutoring — Administrator @ 12:57 pm

Someone recently asked what a zero exponent would mean in the real world. Here is my basic response.

The important method of research is to ask and answer questions, and the important questions to ask are “how did we get the concept?” and “what does it mean?” We should look for things in the world where we take exponents. Where did we start? As far as I know, people started in history with geometry, with squares and cubes. What did we do from there? Include natural numbers as exponents. What did we do from there? Include zero as an exponent. What did we do from there? Include negatives, fractions and irrational numbers as exponents.

But let’s consider squares and cubes. We would multiply a length by a length to get an area; this is why we “square,” and from where the name comes. We would multiply a length by a length by a length to get a volume; this is why we “cube,” and from where the name comes. So a cube is a volume, a square is an area, a first power is a line, and so we could define a zero power to be a what? A point. (Considering 5^0 meter to not be the same as (5 meter)^0, just as they are different for the square or cube.)

The person suggested thinking about the number of apples to the zero power. Apples are not a good example, as I’m thinking. Why would we square or cube or otherwise exponentiate the number of apples?

Better examples would be things we can square or cube, or situations where we do so. One good example is compound interest (and continuous interest). We find that we can multiply a dollar amount by a factor, e.g., (1 + 0.08/12), which would be 8% interest compounded monthly, to get a dollar amount for next year. We can multiply that by the same factor to get a dollar amount for two years out. When we look, we find we could’ve multiplied the original amount by the factor squared, (1 + 0.08/12)^2, to get a dollar amount two years out. And so on for three or four years: (1 + 0.08/12)^3 and (1 + 0.08/12)^4, respectively.

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October 30, 2012

The Pythagorean Theorem

Filed under: Education,Homeschooling,Mathematics — Administrator @ 1:33 pm

Cut-the-knot.org has a page containing what they say are 98 proof of the Pythagorean Theorem. This is a theorem of which people should know a few proofs; it should not be given without any justification, proof, or reasoning; to do so is illogical and irrational, and trains students to do what they are told without understanding — not a good philosophy of education, if what we want our children to become rational, independent adults.

October 29, 2012

Teaching Sequences

Filed under: Education,Homeschooling,Logic,Mathematics,MGTutoring — Administrator @ 9:52 am

Recently, I tutored someone in algebra. In his math class, he was covering arithmetic sequences as an example of functions. In his textbook, there were some applications, but not many and not very good. The presentation was not the worst, but it certainly was not the best.

The book did not give many good examples, it did not contrast arithmetic sequences with anything, it did not relate arithmetic sequences to anything (except, of course, to functions) and it did not motivate the topic by identifying where in reality and human life the concept (and related concepts) come up. There was bad epistemology (see also the Internet Encyclopedia of Philosophy or the Stanford Encyclopedia of Philosophy), bad thinking and teaching methods, all around. Please avoid these mistakes and rectify them when teaching your child or your students!!

To teach properly, to train the rational faculty of a child for adult life or student for professional life, we need to put what we do in context of rational, objective principles of epistemology and in context of practical life and human survival.

So I discussed arithmetic sequences vs. geometric and Fibonacci sequences, and said there were other types. We looked at examples of each type of sequence, to clearly differentiate the three. We saw they were all similar, and so should be classified together, but we saw what differentiated one from another. We looked at some examples of the sequences in real life — finance, bacterial growth, nuclear half-lives, plant and animal growth — so we knew why they were important and something we should study. We had examples that should be relevant to the student’s adult life (and, depending on the student, we provided enough information so that the math-intelligent student should be able to see how they could use some sequences now) and that showed how sequences were important in human life in general.

Then, and only then, we did some work specifically on arithmetic sequences, and did his book work. When we finished, I reviewed some points from the beginning.

We should show students how we develop a concept or method from real, practical experience in the real world, how classification — using similarities, differences, narrower groups/classifications, wider groups/classifications — comes into play and is important, and why the idea is important. It just takes a little time, but has profounds results on a person’s confidence, motivation, ability to reason correctly and logically, and success in life.

Update: To be able to do this, you need to immerse yourself in the material. You need to be a specialist — which is why you should hire a teacher or tutor, just as you would seek out a specialist in medicine,  mechanics, HVAC, electricity, dance, martial arts. Homeschoolers who want to work with their own children should do so, but should seek out a teacher/tutor for guidance. The teacher/tutor could give a lesson or two every week with you there, and you could handle the teaching the rest of the week. Or you could work with the teacher/tutor on your own, then take back what you learned to your children.

September 25, 2012

Geometry in Practice

Filed under: Animals,Business,Homeschooling,Mathematics — Administrator @ 12:25 pm

Dr. Mercola talks to farmer Joel Salatin about how Joel raises his chickens. Tune in at 13 min 55 sec (first video). Also on YouTube.

 

September 13, 2012

Geometry in Design

Filed under: Art,Homeschooling,Mathematics — Administrator @ 9:54 pm

Too cool: geometry in the Apple logo.

July 25, 2011

A Student Speaks

Filed under: Education,Mathematics,MGTutoring,Philosophy — Administrator @ 9:13 am

” ‘Use logic in math’ is my motto.”  — Sophia S (October 31, 2010)

That, and persistent, hard work, are why she gets mostly As. I love that quote.

July 20, 2011

Math Humor

Filed under: Humor,Mathematics — Administrator @ 6:30 pm

HT: Jenny A

July 18, 2011

Pythagorean Triples

Filed under: Mathematics — Administrator @ 10:37 am

Geometry For Enjoyment and Challenge, by Rhoad, Milauskas and Whipple (publishers McDougal Littell/Houghton Mifflin), has some rules for generating Pythagorean triples (see also Mathworld.Wolfram.com) on p. 403:

Rule of Pythagoras: for n an odd number, the triple will be n, (n^2 – 1)/2, (n^2 + 1)/2;

Rule of Plato: for n an even number, the triple will be n, n^2/4 – 1, n^2/4 + 1;

Rule of Euclid: for m and n both even or both odd, the triple will be (m – n)/2, sqrt(mn), (m + n)/;

Rule of Maseres: for m and n any two integers, the triple will be m^2 – n^2, 2mn, m^2 + n^2.

Nice!

July 12, 2011

The Importance of Mathematics: An Example

Filed under: Logic,Mathematics,Philosophy,Science,Technology — Administrator @ 9:22 am

The Lake Peigneur salt dome drilling disaster, which you can read about on Wikipedia and see on YouTube (and on EducatedEarth.com), demonstrates the importance and truth of the dictum “measure twice before you cut once.”

July 3, 2011

Mental Math

Filed under: Education,Mathematics — Administrator @ 8:28 am

On YouTube, Total Breeze has some good videos on mental math: addition, subtraction, multiplication, division, and square rooting. Worth watching.

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