Sabtu, 29 Maret 2008

Giveaway!

Today I have something a little different from the "norm": a giveaway!

All you have to do to take part is go visit Homeschool Boutique, find a T-shirt you'd like to win (these shirts mostly carry homeschool slogans), and then either leave a comment below mentioning the shirt you'd like to win, or email me with your choice.

Just one note: whichever way you do it, make sure I can contact you/find your contact info easily.

We will choose 2 winners by drawing. This contest ends Sunday, April 5, 2008.

Jumat, 28 Maret 2008

Placement tests for Math Mammoth LightBlue Series

I've just added to the site placement tests for the Math Mammoth complete curriculum (LightBlue Series), for grades 1-4. These are actually end-of-year tests. They could also be used as diagnostic tests, to see what content areas a child might be lacking in .

Kamis, 27 Maret 2008

A problem to solve about multiples

Here's one more problem from the collection that John Morse sent me.


144, being a multiple of itself, naturally ends with ...144.

What is the next greater multiple of 144 ending in ...144?


I chose this problem because solving it doesn't require knowing any concepts beyond multiplication and multiples.

I solved this problem kind of a "crude" way; however upon thinking my solution through, it is fairly accessible to even younger students, because it doesn't use more sophisticated concepts.

Basically I considered the problem as finding ABC (A, B, and C are digits), or possibly a longer or shorter number such as 144 x ABC ends in 144.

144
x ABC
-----


I systematically checked what C can be in order for the answer to end in 4.

I found only one possible digit works.

Then I systematically checked what B can be, knowing that C must equal 6 -- and found two possible digits: 2 and 7.

After that, I stumbled upon the right answer since I simply checked what is 26 x 144, 76 x 144 and 126 x 144. The last one is the multiple we're looking for - it is 18,144.

Like I said, this method IS accessible to students who have mastered multiplication algorithm.




Another solution, essentially by John Morse:


This one uses the concept of a "digital root", which means essentially the remainder when dividing a number by 9. You can find it out by adding the digits of a number until you get a sum less than 10.

For example, the digital root of 28,294 is found this way: 2 + 8 + 2 + 9 + 4 = 25; 2 + 5 = 7.
When finding the digital root (or divisibility by 9), you can always "cast out nines" or any combination of numbers adding up to nine - in other words, omit them from the total sum. In the above example, it's enough to add 2 + 8 + 2 + 4 = 16; 1 + 6 = 7 to obtain the digital root.


We're looking for a multiple of 144 that ends in ...144. Since 144 is a multiple of 16, ITS multiples will also be multiples of 16. Similarly, 144 is a multiple of 9, thus ITS multiples will also be multiples of 9 (divisible by 9).

Then, we do know our number will be greater than 1,000. The number we look for is (some thousands) + 144 since it must end in 144. Since 144 is a multiple of 16, those whole thousands tacked to our multiple must be also be multiples of 16. 1000 is NOT a multiple of 16, whereas 2000 (and its multiples, all having even-number thousand's place digits) ARE multiples of 16.


Hence, it remains to find the digits in front of ...144 such that they, placed together, form a multiple of 9 AND 2. The least such digit pair is 1 & 8, putting even digit 8 in the thousands's place, and thus forming 18144.

Selasa, 25 Maret 2008

Lockhart's Lament

Recently there's been a lot of talk about an essay written by mathematician/teacher John Lockhart, called Lockhart's Lament. Some people praise it, some are more skeptical.

Lockhart's Lament makes for good reading and he raises some really interesting points, so I can heartily recommend reading it.

Personally I don't fully agree with every statement he makes there. But his MAIN point concerns mathematics as an art, and how we should teach it.

I went ahead and copied a part of the essay below. This is direct quote from the essay, presenting a VERY GOOD example with the triangle problem.



So let me try to explain what mathematics is, and what mathematicians do. I can hardly do better than to begin with G.H. Hardy's excellent description:

A mathematician, like a painter or poet, is a maker of patterns. If his patterns are more permanent than theirs, it is because they are made with ideas.

So mathematicians sit around making patterns of ideas. What sort of patterns? What sort of ideas? Ideas about the rhinoceros? No, those we leave to the biologists. Ideas about language and culture? No, not usually. These things are all far too complicated for most mathematicians' taste. If there is anything like a unifying aesthetic principle in mathematics, it is this: simple is beautiful. Mathematicians enjoy thinking about the simplest possible things, and the simplest possible things are imaginary.

For example, if I'm in the mood to think about shapes-- and I often am-- I might imagine a triangle inside a rectangular box:



I wonder how much of the box the triangle takes up? Two-thirds maybe? The important thing to understand is that I'm not talking about this drawing of a triangle in a box. Nor am I talking about some metal triangle forming part of a girder system for a bridge. There's no ulterior practical purpose here. I'm just playing. That's what math is-- wondering, playing, amusing yourself with your imagination.

....

The mathematical question is about an imaginary triangle inside an imaginary box. The edges are perfect because I want them to be-- that is the sort of object I prefer to think about. This is a major theme in mathematics: things are what you want them to be. You have endless choices; there is no reality to get in your way.

On the other hand, once you have made your choices (for example I might choose to make my triangle symmetrical, or not) then your new creations do what they do, whether you like it or not. This is the amazing thing about making imaginary patterns: they talk back! The triangle takes up a certain amount of its box, and I don't have any control over what that amount is. There is a number out there, maybe it's two-thirds, maybe it isn't, but I don't get to say what it is. I have to find out what it is.

So we get to play and imagine whatever we want and make patterns and ask questions about them. But how do we answer these questions? It's not at all like science. There's no experiment I can do with test tubes and equipment and whatnot that will tell me the truth about a figment of my imagination. The only way to get at the truth about our imaginations is to use our imaginations, and that is hard work.

In the case of the triangle in its box, I do see something simple and pretty:




If I chop the rectangle into two pieces like this, I can see that each piece is cut diagonally in half by the sides of the triangle. So there is just as much space inside the triangle as outside. That means that the triangle must take up exactly half the box!

This is what a piece of mathematics looks and feels like. That little narrative is an example of the mathematician's art: asking simple and elegant questions about our imaginary creations, and crafting satisfying and beautiful explanations. There is really nothing else quite like this realm of pure idea; it's fascinating, it's fun, and it's free!

Now where did this idea of mine come from? How did I know to draw that line? How does a painter know where to put his brush? Inspiration, experience, trial and error, dumb luck. That's the art of it, creating these beautiful little poems of thought, these sonnets of pure reason. There is something so wonderfully transformational about this art form. The relationship between the triangle and the rectangle was a mystery, and then that one little line made it obvious. I couldn't see, and then all of a sudden I could. Somehow, I was able to create a profound simple beauty out of nothing, and change myself in the process. Isn't that what art is all about?

This is why it is so heartbreaking to see what is being done to mathematics in school. This rich and fascinating adventure of the imagination has been reduced to a sterile set of "facts" to be memorized and procedures to be followed. In place of a simple and natural question about shapes, and a creative and rewarding process of invention and discovery, students are treated to this:



"The area of a triangle is equal to one-half its base times its height." Students are asked to memorize this formula and then "apply" it over and over in the "exercises." Gone is the thrill, the joy, even the pain and frustration of the creative act. There is not even a problem anymore. The question has been asked and answered at the same time-- there is nothing left for the student to do.

Kamis, 20 Maret 2008

Assortment of links and news

I have quite a collection of links and stuff people have sent me. Hopefully everyone will find something of interest!




Esp. for teachers

  • LearnHub is a network of communities, each one built around a specific subject.

    You can do all kinds of stuff: upload videos, author pages using a simple editor, upload your powerpoint presentations, create tests and track users' progress, combine lessons, tests, and activities into a restricted access course, complete with e-commerce integration. Learnhub also includes live tutoring, live video, voice, whiteboard and document sharing.

    If you want to teach something online, this website sounds really interesting.


  • WorksheetLibrary.com contains
    thousands of worksheets for all school subjects and levels. This is a subscription service, but you'll find some free worksheets in every area.



For all math enthusiasts

Some math software!

  • First of all, some real "heavy" machinery for serious computing:

    SpaceTime 3.0 is now available for Windows, Pocket PC, Smartphones, and Palm handhelds. It is the most powerful mathematics software available for mobile devices at very affordable prices and has many of the features of top commercial programs such as Mathematica and MATLAB including a built in scripting engine.

  • From the same place, MyCalculator is a free scientific calculator for Windows, Pocket PC, Palm handhelds.



For all of us who like to voice our opinion (or vote)

There is one week left in the contest for images to represent the Carnival of Homeschooling. So go vote - only seven days left!

Vote for whatever size image
Vote for medium size image

Rabu, 19 Maret 2008

Math Mammoth Introduction to Fractions

A new book for the Blue Series, Introduction to Fractions has simple fraction lessons with lots of picture-based visual exercises, and small denominators.

Learn more at the above link.

Senin, 17 Maret 2008

7 things you'd never guess about me

I got tagged by Sol for a meme "7 things about me you'd not likely guess".

Here goes:

1. When I was in elementary school, I wanted to become a nurse (probably because my mom was one).

2. When in middle school, I wanted to become an elementary school teacher. I was pretty sure I'd do that. Math was NOWHERE in my mind. I didn't mind math but I didn't think of it as anything especially interesting either. In fact, I wouldn't have chosen math had it not been for some coincidences...

3. One happened in 9th grade. One of the math teachers (who didn't teach me) saw my score in the national 9th grade math competition, and persuaded me to choose the longer math course for high school... Originally I was going to go with the short math, no physics, and two languages. So I changed the shorter math course to the long one.

4. Another strange coincidence: when high school started (10th grade), the first day of school I was told they had accidentally put me in the wrong class... that because I had the longer math course without physics, that I'd belong to the group "B" and would have to change OR take physics. My friends were in the group "A" so I didn't want to go to group "B". So I chose physics and dropped one foreign language. So this is how I "ended up", as if by accidents, with the right background (physics and math) in the high school to be able to study math in the uni.

5. My math teacher in 10th grade (1st year of high school) was really nice and good and kept talking how there is going to be a lack of math teachers in years to come. During that year I figured I would study math after high school.

6. I almost became a piano teacher as well, because I was studying it half-time alongside math. But one sunny morning it was as if something went to my ears and I couldn't stand any loud noises at all, surely not my own banging of a grand piano in a small room. The doctors never found anything and suspected some kind of an infection went to my ears from a cold I had had two months previous. To this day, it is a mystery what exactly happened but it "killed" my piano teacher career.

7. All through my growing up and schooling, I always thought I'd work for the school system. My dad worked for the postal system, my mom was a nurse, all my friends parents worked for someone else... Thus, it NEVER crossed my mind I would become an entrepreneur, independent of the "systems". But here I am, doing just that.

If you have a blog and like this meme, consider yourself tagged!

Minggu, 16 Maret 2008

Movies of math in the real world - FuturesChannel.com

I delved into this fascinating website just this past week, and I heartily recommend you visit it, too!

Most math teachers have faced the age-old question, "When will I ever need this?", especially when kids get into algebra and more. Well, FuturesChannel.com has the answer - in the form of short movies, lesson guides, and worksheets.

The topics are just fascinating, from skyscrapers, roller coasters, endangered animals, to inventing, the subway, bakery, bicycle design, etc.

For each movie, there is a worksheet or several for the student that concentrates on some math topic that is needed in the field shown in the movie.

Some samplings:

100,000 computers a day
A rare and fascinating look inside the world's largest computer manufacturer, Dell Inc., where thousands of computers are custom-built and shipped around the world every day. From the call center to the inventory system to the assembly line and beyond, one thing is certain: The whole operation relies on a variety of math skills every step of the way.

Inventing with Polygons
This guy had some really interesting stuff! Inventor Chuck Hoberman uses polygons to build amazing expandable structures.

Structural Engineering
To design buildings that don't fall down, you need to know how your materials will respond to forces such as gravity, wind, and earthquakes.

The Bakery
Whether it's fractions or measurement or division, a key ingredient to this baker's success is math, making each one of his pastries, cakes and breads as delicious as the last.

Jumat, 14 Maret 2008

Listen to your Pi!

Today is Pi day (3/14 or March 14) and to celebrate it, you can LISTEN to your Pi!




My hubby said the music is pretty good but needs a chorus...

And here are a bunch more links for celebrating Pi day... from Let's Play Math.

Rabu, 12 Maret 2008

Silly Sentences and carnival time

Homeschooling Carnival is online at At Home with Kris. There's a special section on the recent situation in California.

Some picks: since I have a preschooler at home, I went to check Have Fun with Sentence Structure, only to find SisterLisa explaining how much DK's game Silly Rhymes had helped her daughter.


Well, that I can chime in with, because we recently bought a very similar game, called "Silly Sentences" and my preschooler is LOVING it! In fact, in the mornings when she wakes up she tends to go directly to the drawer where we keep it and start playing.


Senin, 10 Maret 2008

HomeschoolEstore is now CurrClick

HomeschoolEstore.com has changed its name and from TODAY on it is called CurrClick.com - curriculum in a click! CurrClick carries electronic curriculum products catered especially to homeschoolers.

They have a grand opening lasting for a week, during which you get a 10% account credit on every purchase you make.

here's a link directly to my Math Mammoth books at CurrClick.com:

Math Mammoth at CurrClick

Or, click below to enter their home page:



I also want to mention.... they have an affiliate program. So if you like my books (or other products there), and want to promote them, you can earn credit at CurrClick by joining their affiliate program and posting banners/links on your website or blog.

During this week only, you get 15% on every purchase you initiate as an affiliate. I think the normal percentage is 10%.

Kamis, 06 Maret 2008

A triangle problem to solve

I have another neat problem for you to solve. This one should be accessible to middle schoolers on up.

The sides of triangles A and B measure 5, 5, 8 and 5, 5, 6 respectively. What is the ratio of the area of triangle A to that of triangle B? Express in simplest a:b form.


This problem is original to John Morse. He is a local mathematics researcher/
author/tutor/computer programmer in Delmar, NY, and has written this problem to help learners use creative and problem-solving skills in various ways. And I think this problem can indeed help in that - it can be solved in many different ways.

[update - solution follows]

I like this problem because there are many ways to solve it and to use it with different grade-level students - such as is already mentioned in the comments.

1) You could use this as a drawing and measuring exercise with 6th or 7th graders who have learned to do compass and ruler constructions.

Once they know how to construct a triangle given its three sides (or see here as well), they can construct these two, then draw & measure the altitudes, and calculate the areas.

Of course the downside is that measurements are bound to be inaccurate, and so they are unlikely to get exactly 12 square units as the area. But then again, you could discuss this topic as well (inaccuracy of measurements).


2) Another way to (clumsily) solve this is to calculate the areas of the two triangles using Heron's formula (if you know it exists!) Just plug the numbers in.

3) The elegant way... accessible to students who know about Pythagorean Theorem. I'll take you through it step by step.

The first step is to NOTICE that the triangles are isosceles ("same-legged"), and to draw a sketch.

(Mine is not a "rough sketch" but as exact as can be done in PhotoImpact, because I started out by drawing the three sides with the given lengths. Then I calculated one angle, and turned one side in that angle to get a "corner".)


In order for the students to easily see the solution, it is fairly important to be able to sketch the two triangles.

When drawing isosceles triangles, think of the capital letter "A" and its two "legs". We just need to draw one that "stands" taller and one that "stands" with its legs wider open.

Notice one of them is close to an equilateral triangle since it's sides are "almost" the same.. 5, 5, and 6. So you would sketch it as almost an equilateral triangle, just make those "legs" to open a little more. Then the 5-5-8 triangle needs to open its "legs" quite wide to make for the wide 8-unit base.

556-558-triangles

Now, we are concerned about their AREAS, so naturally we need an altitude. Once you draw the two altitudes, the idea is usually to find how many units long the altitudes are, so you could calculate the area.

But in this case, there's sort of a shortcut. You will realize (or remember) that the altitude forms two little RIGHT triangles in each triangle.

556-558-triangles

In the triangle on the left, the two known side lengths of the little triangle are 5 and 3, and in the other the two known lengths are 5 and 4.

This would HOPEFULLY ring a bell.... DING! REMEMBER the 3-4-5 right triangle? Would it fit here?

Oh yes, it does. In BOTH triangles, the little triangles are 3-4-5 right triangles!

To prove it, you CAN use the Pythagorean theorem: in one little triangle, you'd have x, 4, and 5 (5 being the hypotenuse), so solving x2 + 42 = 52 gives you x = 3, and in the other triangle, solving x2 + 32 = 52 gives you x = 4.

But there's no need to go through the solving if you remember that 3-4-5 is a right triangle.

556-558-triangles

OK, now we know the altitudes and could calculate the areas... BUT wait! If the little triangles are identical (congruent), then their areas are the same, and the areas of the large triangles are the same as well. We only need to find the ratio of the two areas, not the actual areas.

So with two triangles with the same area, the ratio is of course 1:1.