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Surf for More Math

Lesson 5 - Congruence and Similarity


To encourage students to have fun on the Web while learning about Congruence and Similarity, here are some games and interactive activities they can do on their own or in pairs.


Investigate the conditions that make two shapes congruent or similar.

Builds Upon

Student Book pages 244-245

Instructions for Use

Geoboard allows students to create congruent or similar shapes.

To use Geoboard, select a circle by holding the mouse button down, and drag it to any location on the gird. Release the circle to anchor it. A red node appears at the top of the circle. Click on any part of the circle and drag it in any direction. It will stretch much like a rubber band. Secure the band to any points on the grid. You can make many geometrical shapes.

Click on the circle again to add as many bands as you like. To colour the area in the shape, click first on the shape and then on the colour buttons to the right. To release a node, hold the Ctrl key down and click on the node. Click on the "Delete Node" button to delete each node. Click on the "Delete band" button to delete each rubber band. Click on the "Clear" button to start the exercise over again.

Have students create congruent shapes and similar shapes with the Geoboard.


Congruent Triangles helps students identify congruent triangles.

To use Congruent Triangles, input all the names of the triangles and congruent shapes in the text fields provided. Click the "Check Answer" button for your results.


Congruent and Similar Shapes helps students identify what make shapes congruent or similar.

To use Congruent and Similar Shapes, have students read the website.


Triangle Relations lets students investigate what conditions make two shapes similar or congruent.

To use Triangle Relations, drag any vertex of either triangle to reposition it. Use SHIFT-Drag to reposition any vertex of either triangle. Then drag the highlighted location in the interior of either triangle to reposition the entire triangle. Click the side of a triangle to reflect the triangle. Drag the faint horizontal line through the highlighted location in the interior of either triangle to rotate the triangle. Drag the faint vertical line through the highlighted location in the interior of either triangle towards or away from the highlighted point to re-size the triangle. Use CONTROL-Drag on any location in the graph area to rescale the triangle sides towards or away from the center of the triangle.