Optimizing Coverage: Security Cameras

Mathematical goals

This lesson unit is intended to help you assess how well students are able to:

  • Analyze a realistic situation mathematically.
  • Construct sight lines to decide which areas of a room are visible or hidden from a camera.
  • Find and compare areas of triangles and quadrilaterals.
  • Calculate and compare percentages and/or fractions of areas.


The lesson unit is structured in the following way:

  • Before the lesson, students attempt the Security Cameras task individually. You review their responses and formulate questions for students to consider in order to improve their work.
  • At the start of the lesson, students respond individually to the questions set. They then work in small groups to produce a joint solution to the Security Cameras task, in the form of a poster.
  • In the same small groups, students evaluate and comment on sample responses, identifying the strengths and weaknesses in these responses and comparing them with their own work.
  • In a whole-class discussion students compare and evaluate the methods they have seen and used.
  • In a follow-up lesson, students reflect on their work and what they have learned.

Materials required

  • Each individual student will need a copy of the assessment task Security Cameras, a mini-whiteboard, a pen, and an eraser. Provide rules if requested.
  • Each small group of students will need at least two copies of the Plan View, a sheet of poster paper, felt tipped pens, a glue stick, and copies of Sample Responses to Discuss.

There is a projector resource to help to introduce activities and support whole-class discussions.

Time needed

20 minutes before the lesson, a 90-minute lesson (or two 50-minute lessons) and 10 minutes in a follow-up lesson. Timings given are only approximate and will depend on the needs of the class.