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Maria's Math news - a FREE math newsletter for parents and teachers

May 2013

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This is where you'll find the latest happenings, news, & ideas in math teaching

Math teaching videos
My videos at YouTube show you how to teach concepts.
How to help students with multiplication tables?

Worksheets
Various worksheets on TONS of math topics you can generate for free!

Basic operations worksheet generator is updated! Make worksheets for whole numbers or integers - all four operations, including add & subtract or multiply & divide - horizontal or vertical - add a border and/or extra workspace, use a variable, and more.

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Advice, reviews, and resources to help you choose a math curriculum!

Online math games, tutorials, and activities
Games you can play online, interactive tutorials, fun math websites and more. Arranged by topic/level for ease of use.

Lessons
Learn how to TEACH concepts or about general concerns in math education.

Reviews
In-depth reviews of math products

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A list of free message boards, math help websites, and online tutoring services.

Fun and games
I have two games on my site, plus links to many.

(easy hangman)
(difficult)

The ideas in this geometry lesson are taken from Math Mammoth Geometry 1 book.

Area of right triangle
Free geometry lesson plan from HomeschoolMath.net

In the following pictures the rectangle is divided up into two right triangles.
The thus formed two right triangles are identical in the sense that if you could
move them on top of each other, they would exactly match.

This rectangle has the area of 2 × 4 = 8. How could you find the area of the two triangles?
Here the area of the whole rectangle is 3 5 = 15. How could you find the area of the two triangles?
Here the one side of the triangle is 4, and the other side is 3. The corresponding rectangle is shown with dotted line. How can you find the area of the triangle?
Can you figure out what the area of this triangle must be?

Let us look closer at the last triangle in the previous paragraph. Hopefully you figured out that its area is 12. To confirm that we can actually count the little squares in the triangle. Note that some parts don't form a whole square, but combining them we get whole squares and can then count them.

[picture omitted from Free lesson plan; available in the ebook]

The area of a right triangle is

SIDE × SIDE

because it is exactly _________ of the area of a rectangle.

Example problem types

1. Find out the area of the following right triangles.

2. Here you see two different shaped
right triangles that both have the area of 10:

In each case draw 3 different right triangles that
have the area of
a) 6 b) 9 .c) 12 d) 15.

Next geometry lesson

New! Times Tales is now on DVD!

The fast, FUN, and easy way to learn multiplication. Learn the upper times tales in two sittings using mnemonic stories.

Area of right triangle Free geometry lesson plan from HomeschoolMath.net

Example problem types

Area of right triangle
Free geometry lesson plan from HomeschoolMath.net