What this unit is about

Estimation is an integral part of our daily lives because, in most contexts, we are more concerned with an estimate rather than the exact value of any measure. For example, if we are to go from destination A to destination B, we are interested in estimating the duration of the journey rather than the exact time of completion.

Repeated attempts to estimate the same quantity make our estimates better. For example, a fruit juice vendor (Figure 1), through experience, can estimate very accurately the number of oranges from which they can extract five glasses of juice.

Even so, students often ignore the process of estimation and work out the exact answer instead – even when specifically asked not to. Because they are not confident estimators, they do not have the tools to help them realise when their calculated answers are not plausible.

In this unit you will focus on how to teach estimation as a tool for working on mathematical thinking and for making fewer errors in mathematical calculations. The activities will ask your students work on their mathematical thinking processes and on clarifying these through discussion.