Evaluating Statements About Enlargements

Mathematical goals

This lesson unit is intended to help you assess how well students are able to solve problems involving area and volume, and in particular, to help you identify and assist students who have difficulties with:

  • Computing perimeters, areas, and volumes using formulas.
  • Finding the relationships between perimeters, areas, and volumes of shapes after scaling.


The lesson unit is structured in the following way:

  • Before the lesson, students work individually on an assessment task that is designed to reveal their current understanding and difficulties. You then review their work and create questions for students to answer in order to improve their solutions.
  • After a whole-class introduction, students work in small groups. They consider the results of doubling the measurements of a range of shapes in two and three dimensions.
  • After a whole-class discussion, students return to their original task and try to improve their own responses.

Materials required

  • Each individual student will need two copies of the assessment task A Fair Price, and a mini-whiteboard, pen, and eraser.
  • Each small group of students will need the True or False cards (cut-up), the Formula Sheet, a large sheet of paper, and a glue stick.
  • Calculators should be made available for students who request them.
  • There is a projector resource to help with whole-class discussions.

Time needed

15 minutes before the lesson, an 80-minute lesson (or two 45-minute lessons), and 15 minutes in a follow-up lesson. Timings given are approximate. Exact timings will depend on the needs of the class.