Linear Measurement

Today we began our linear measurement unit with a 'Minds On' diagnostic activity. Students were given a piece of string and asked to construct a triangle or quadrilateral with the string on their desktops. The two ends of the string had to touch but not overlap. Using their rulers to measure in centimetres, students were asked to find the perimeter of their shape. This gave me the opportunity to observe who understands perimeter as a measurement of the distance around a shape, and which students already know how to calculate the perimeter by adding together the lengths of each side of their shape. I was also able to observe how effectively they use a ruler to measure and whether or not they start measuring at the zero mark, etc. Next, I asked them to construct a similar shape but with a smaller perimeter. I reminded them that at the beginning of the task, I had also provided them with a pair of scissors! I was able to make observations about their proportional reasoning skills and I am happy to say that most students quickly figured out that they would need to cut their string shorter in order to create a shape with a smaller perimeter. When I asked them whether or not they would like to repeat this activity but instead use metres to measure, they quickly scoffed at this idea, telling me that metres are WAY too big a unit for this task and that their desks aren't even a metre wide! We discussed measuring the perimeter of the schoolyard and decided that metres would be appropriate for that task and that kilometres would be too big to measure the perimeter of the school property. It was a fun initial exploration of linear measurement. A reminder that all of the key concepts to be covered in the unit, can be found in the 'Sum it Up' pages that have already been sent home.