## Saturday, April 6, 2013

### Finding Area of Parallelograms with the Geoboard (App!)

We've been working on a free lesson from the Math Learning Center, "Area of Parallelograms." (See Supplement D9.) On a regular geoboard it took a lot of rubberband maneuvering to figure out how to change a rectangle into a non-rectangular parallelogram and keep the same area. We decided to use the (free) Geoboard App to make it easier. (Available in both online and app versions.)

To the above right, you can see the original rectangle.  Below you'll see the rubberband movement that resulted in a non-rectangular parallelogram. I took a photo and quickly scribbled down how my student calculated the total area. You'll notice that he combined the sides to calculate the area.

In my more recent math education (teaching!) it's been enlightening for me to use manipulatives like this to calculate area of shapes.

Here, you might calculate area by first seeing a triangle as a part of a larger rectangle. In the photo at left, you can see a rectangular area of 3 square unit. If you divide those 3 square units in half (with the orange rubberband), you're then left with 1.5 square units. (So 1.5 square units on each side of the parallelogram above.)

Who knew it was so easy to calculate area? :)

1. Yep, yep, yep! Saw that app the other day, requested it be added to our student iPads and used it for area lessons as well. GREAT APP!

Mrs. Jones :)

1. Sarah, I hope you post what you do with the app. I'd love to see other examples! :) Thanks for sharing.

2. What an awesome tool! I'm featuring this post on Bagels and Blogs tomorrow. :)

Donna
Math Coach’s Corner

1. Thank you, Donna! I love Bagels and Blogs. :)

3. I can't wait to try this when we start geometry in a couple of weeks! I hate dealing with those rubber bands; at least one friend always manages to shoot one across the room! No Ipads :( but we will use the web version.
Carol
Still Teaching After All These Years

1. Carol, this has made using the geoboard so much easier for me! I've also found that some kiddos just can't manipulate geobands very well. And this is easy. Hope you come back and post after using them. I'd love to read what you do and how it goes...

4. >Who knew it was so easy to calculate area? :)

You didn't mention what grade this class is, but area problems are not always so "easy":
http://fivetriangles.blogspot.com/2012/04/area-problem.html

1. No doubt. :) This was a fourth grade lesson.

Thank you for leaving me a message. I love comments almost as much as I love chocolate! And I do LOVE chocolate. :)

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