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! I look forward to your reply. Thanks so much!
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, you might start with a few rectangular sandwiches and show cutting 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/
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