Sometimes it is difficult to relate mathematics to our monthly themes. Sometimes our theme works beautifully well - as in the case of this month's theme of Cities. When I think of cities, I think of buildings, which leads to materials and measurement (especially perimeter and area). So for the next couple weeks at least, my math group will be learning how to measure area and perimeter of rectangles, the reason that we need to use standard units of measurement, and getting practice using rulers to draw, design, and measure. We will also revisit the idea of scale.
Yesterday, I checked to make sure students could articulate what we mean by perimeter. I was actually surprised that not many could. While some could trace around something with their hand, or knew it had something to do with the "edge", they were obviously not comfortable with giving a clear definition. For our purposes, I am defining perimeter as: The distance around a two-dimensional shape.
Today, after workbooks were put away, we confirmed that we knew what perimeter means, and also talked about non-standard units of measurement. I gave the example of wanting a new bookshelf for the classroom. I could measure it with my hands and give these dimensions to the carpenter. But suppose the carpenter was a huge guy with big ol' hands - would the bookshelf be the size I wanted?
I then assigned children or pairs of children to measure the perimeter of something. I chose what they were to measure, but they got to choose the non-standard unit of measurement. Children were measuring with erasers, pencils, pillows, scarves, and LEGO. They then wrote down their measurements, making sure to name the object measured, the perimeter, AND the unit of measure. We are really working writing the unit when we talk or write numbers, so this was good, realistic practice.
Some of the interesting perimeters we came up with are:
The ottoman is 11 tissues boxes in perimeter, while 39 erasers around. The bookcase has a perimeter of 52 stretchy bands (unstretched). The library rug has a perimeter of 38 tissues boxes, or 9 1/2 scarves, while the chalkboard's perimeter is 88 glue sticks.