Area of a Circle Lesson 2: Rounding out Area

Australian curriculum number (ACMMG197)

Lesson abstract

The lesson consists of three stand-alone activities that, in different ways, consolidate students’ knowledge of the formula for the area of a circle.  The first activity provides pictures of circular objects in the outdoors for students to estimate the areas. The second activity enriches students’ class textbook-based practice with the circle area formula by illustrating the variation that is required for comprehensive understanding. The third activity, Precious Pendants, provides challenging multi-step area calculations and an opportunity for creativity.   

Mathematical purpose (for students)

The area of a circle can be estimated or calculated exactly using the formula, for many practical applications. 

Mathematical purpose (for teachers)

This material builds students’ skills with computation and estimations involving circle area in many variations.  Together these ideas present a comprehensive view of the use of the formula for the area of a circle. Students calculate area from the radius or diameter and vice versa. The areas of compound shapes are calculated and some complex problems are solved. Students calculate with measurements given in a range of forms – whole numbers, fractions and decimals with differing numbers of decimal places. Sensible limitations of accuracy of answers can be discussed.