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Surf for More Math

Lesson 6 - Calculating the Area of a Complex Shape


Use this interactive activity to encourage students to have fun on the Web while learning how to calculate the area of a complex shape. Students can try this activity on their own or in pairs.


Calculate the area of an irregular 2-D shape by dividing it into simpler shapes.

Builds Upon

Student Book pages 172-175

Instructions for Use

Touch Pegs prompts students to investigate how to calculate the area of a complex shape.

To use Touch Pegs, select a blue band under "Bands" then drag it to any location on the grid. Release the band to anchor it. A red node appears at the top of the band. Click on any part of the band and drag it in any direction. It will stretch like a rubber band. Release the band to secure it to a point on the grid. Secure the band to other points on the grid to form an irregular 2-D shape.

To change a corner of the shape, release a node by holding down the "Ctrl" key and clicking the node. To colour the area inside the shape, click on the shape and then click one of the colour buttons to the left of the grid.

Calculate the area of the shape you created by dividing it into simpler polygons such as squares, triangles, and trapezoids. Click the "Measure" button to check your answer. Click on the "Clear" button to start the exercise over again.