Course Guide - USAID Teacher Education Project

life situations every day. Therefore, we will begin with polygons so that children willbegin to see how angles relate to the shapes they see around them.This is why this third week of the Geometry Unit begins with area, then moves toperimeter, and finally explores the relationship between the two.Two-dimensional shapes are not all polygons. They might be irregularly shaped, suchas a lake, one's hand, or a circle. When trying to measure the area of these shapes, it isimportant that pre-service teachers understand the major mathematical concept that ameasurement is always an estimate.Measurement also depends on determining a unit of measurement (which could bestandard such as a centimetre, or non-standard such as a paper clip) and then repeatingthat unit. For adults, this seems obvious, but confusion about this occurs not just withsmall children but also with older youngsters.Session 2 is devoted to perimeter. The classroom approach begins with a hands-onexperience: exploring perimeter by "wrapping" objects with string and then using aruler to measure the string's length in order to determine perimeter.Session 3 addresses the relationship between area and perimeter. The idea of "samearea, different perimeter" will be explored in a simple manner by using graph paper.If I trace my hand with fingers closed, I can estimate my hand's area and perimeter.But what happens when I extend my fingers? What does this new tracing look like?What is the area of this new drawing? What is its perimeter? How are the twotracings the same? How are they different?To explore the opposite concept, "same perimeter, different area," something assimple as a large loop of string or yarn can be illustrative. The string is a givenperimeter. But when held by a group of four students, it can be shaped intoquadrilaterals with various areas.