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### Teaching Area of Triangles

```
Date: 9/15/96 at 19:40:49
From: MS DAPHNE M BROWN
Subject: Area of a Triangle

I am teaching fifth grade math for the first time.  We have been
studying geometry, specifically area, for the past week.  However,
when I gave a Unit Assessment, all but one student got area of a
triangle wrong. Where did I fail?  Can you help me learn a better
way to teach area of a triangle?  Initially we used geoboards and
found the area of rectangles and squares.  Then we proceeded to
triangles.  I introduced the formula A=bh/2.  Help!

```

```
Date: 9/18/96 at 19:17:25
From: Doctor Jodi
Subject: Re: Area of a Triangle

Hi there! Don't worry that your students haven't grasped the material
as quickly as you thought they would.  It doesn't mean that you've
failed as a teacher, it just means that your students need more
practice with the concepts.

Find innovative ways to relate rectangles to triangles.  For example,
each in half.  Compare triangular sandwich halves with the entire
sandwich and with sandwiches cut in half in other ways.  You could
also have students do similar activities with paper after
demonstrating with a more memorable material.

Then you might want to move on to isosceles triangles, showing how you
can divide the triangle with the perpendicular bisector into two
congruent parts.  Then you can do similar experiments by cutting the
triangles along the perpendicular bisector and fitting them into
rectangles.  Discuss the relation between each smaller triangle, the
entire triangle, and related rectangles.

Finally, use perpendiculars to divide scalene triangles into right
triangles and relate them to TWO rectangles, rather than just one.

You might also try searching the internet for lesson plans.  One good
place to start is the Math Forum's Internet Mathematics Library at:

http://mathforum.org/library/

Best luck and let us know if we can help again!

-Doctor Jodi,  The Math Forum
Check out our web site!  http://mathforum.org/dr.math/
```
Associated Topics:
Elementary Geometry
Elementary Triangles and Other Polygons
Middle School Geometry
Middle School Triangles and Other Polygons

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