Math Journal Sundays

There's just something about Sunday mornings - sitting on the couch with my laptop and coffee, kids quietly playing (for now) - that makes me think I can accomplish anything today ... (which is a good thing because I'm going to need that positive attitude later when I attempt to do some cleaning around here, and make a big yummy lasagna for supper, and fold what will feel like one million cootie catchers for Valentine's Day).

Anyhow, before I tackle the mess I call home, I've got a fun math activity to share for math journal Sundays.  Actually, my post will cover the whole math lesson, but the lesson ended in a fun little foldable.  

We've been studying the relationship between perimeter and area, and I thought it was time to go a little more hands on.  I handed out medium-sized sheets of construction paper, and we got started.

I asked each student to construct (we talked about using a ruler and a protractor to be precise) a rectangle with a perimeter of 90 cm.  When all students had done this, I posted one of them on the blackboard.  

I didn't tell them what dimensions to use because I wanted to have a variety of shapes.

They then had to use the formula to solve the perimeter (on the front of the rectangle), and area (on the back of the rectangle).

I then went around the room, and we discussed the different areas of the rectangles.  We then posted them on the board (smaller areas on the one side, and larger areas on the other side).  And voila!  The students had a strong visual reference as to what shapes of rectangles have the smallest and largest areas, as all rectangles had the same perimeter.

The students came up with the "big idea", which we wrote on the bottom of the chart paper - "When the rectangles have the same perimeter, the closer the shape is to a square, the greater the area".

But that's not all.  I wanted to move on to the area of a triangle, so I had the students get their rectangles off the blackboard, and draw a diagonal on them.  They then cut down the diagonal to make two triangles the same size.  When I asked them what the area of their triangle was, they knew immediately that the area was half of what the rectangle was.  Using one of the triangles, they then solved the area, using the formula.  I had so many students tell me how easy this was, I had to pass around my Easy button for them all to press.  (LOVE it)

We finished off the lesson with a great little foldable for our math journals.  I had them cut out a square, and fold it in half into a triangle.  They glued this into their journals, and solved for the area of the triangle and the rectangle (square).  

You know those rare occasions when you just KNOW the lesson went absolutely perfectly - well, this was one of those times.  I was so happy with the final results, and I KNOW all my students were engaged and learning. Just look at the distribution of sticky note exit slips on our learning goals at the end of the day ... I think they liked the lesson.  ;)

Happy, Happy Sunday!!!

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