Maria's Math News, Vol. 60, February 2012
I love teaching, and I love math. This newsletter is my way of reaching out and helping you to teach it, too.
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Welcome to February! I hope I found "something for everyone," again!
~Maria
1. Math Mammoth sale notices
2. Triangle puzzle - equal areas
3. Vi Hart and mathematical doodling
4. Compound interest
5. Geometry videos
6. Tidbits
1. Math Mammoth sale notices
Homeschool Buyers Co-op will run a (traditional) group buy for Math Mammoth through the month of March.And for those of you that missed my three-day sale in January, I'll run another in late February! But no, this won't become a monthly habit after that.
2. Triangle puzzle - equal areas
Basically, we have a triangle DFE inside a rectangle, dividing the rectangle into various triangles. And, the three areas of fainter color are equal. That is, the area of the triangle DAE = area of the triangle EBF = area of the triangle FCD. (Notice the image is not drawn to scale at all.)
And, we're asked to solve the RATIOS AE : EB and BF : FC.
The solution is posted here.
3. Vi Hart and mathematical doodling
I just learned about Vi Hart's "doodling in math class" videos.Vi calls herself mathemusician - and definitely, she's a talented and smart gal! I'm sure you'll enjoy her videos (as long as you can follow her super fast speeaking). Here are some that I enjoyed:
Doodling in Math: Spirals, Fibonacci, and Being a Plant [1 of 3]
(Also, here's a link to learn more about Fibonacci numbers in nature, so you can read about it at a slow pace : ) )
Binary Hand Dance was pretty cool too!
Her series of "mathematical doodling" videos have become somewhat of a viral success. Here's one more:
Doodling in Math Class: Infinity Elephants
You can also see these three videos on my blog.
4. Compound interest
Someone sent me in a question concerning compound interest...Please send me the formula for compound interest and explain line by line.The formula that this person is using is correct... the formula for compound interest is
p(1 + rate)3
What does the 1 stand for and must you add it to the rate of say 10%?
100(1+10)3 years = ???
Obviously I am looking for a basic course?
A = p(1 + r)t
but this formula doesn't give us the amount of interest -- it gives us the amount of money you would withdraw after t years. In the formula, p is the original principal, r is the interest rate, and t is the time in years.
However, we cannot put the interest rate in as he did. If r = 10%, then r = 0.1 must be used in this formula. In other words, FIRST convert your percentage into a decimal.
Read more
5. Geometry videos
I have expanded the list of 4th-5th grade geometry videos that are available for you to watch! The topics include now:- Lines, rays, and angles
- How to use a protractor to measure & draw angles
- Estimating angles
- How to draw a right angle (perpendicular line) and a rectangle
- Parallelograms
- Acute, obtuse, and right triangles
- Circles
- Polygons—introduction
- Perimeter
- Area of rectangles
- Area versus perimeter
- Volume of a rectangular prism and cubic units
- Angles in a triangle ddd up to 180 degrees
- Angles in a Parallelogram
- Vertical angles
Enjoy! Hope they are of help.
6. Tidbits
- FREE e-book "All Children Can Be Great Listeners"
The e-book outlines a simple, 3-step plan for immediately improving any child's listening, and the e-book also includes 12 activity suggestions and 20 worksheets that are designed to be fun and engaging for kids - while helping them hone important listening skills! (This is meant for Kindergarten level).
- Versa Ruler
Well, this IS something different! A physical ruler that can draw shapes with any angle measure you want. This ruler give you accurate measurements for every side and angle. You can connect sides to form angles, which scale and skew smoothly, and you can lock angles and sides. Unfortunately it's not yet in production. In fact, the project is needing funding... but very interesting!
- The 1-2-3 Song
Bon from Math is not a four-letter word made this little counting song, sung to the tune of "Twinkle Twinkle Little Star". Hope your little ones enjoy it!
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Till next time,
Maria Miller