Congruent figures: the correspondence definition
- Sorting five cards — 3 tasks
- Decide the matching before you write — 3 tasks
- Six statements, and the order of the letters — 3 tasks
- When more than one matching works — 3 tasks
- Going Deeper — 3 tasks
- Practice — 20 tasks
- Summary — 2 tasks
- Cool-down — 3 tasks
Classroom activities
Things a class does rather than writes on. Each one is a finished PDF: print it, cut it up if it says so, and hand it round.
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Congruent, or What Does Not Match? — Cut & Glue Sort 25 minutes, including the cutting · 5 sheets
12 pairs of shapes with their side lengths and angles, sorted into congruent, not congruent because a side does not match, and not congruent although every side matches — a square and a rhombus, a rectangle and a parallelogram — while mirror images and a square turned into a diamond wait in the first row.
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Congruent or Not? Look Again — Answer Maze 10–15 minutes · 4 sheets
8 boxes on one page, each a pair of shapes with their numbers: a mirror image, a square turned into a diamond, a near miss, an enlarged copy, two rectangles of one area. A wrong answer is the mistake the lesson exists to stop, and it goes to a box that sends the student back; the row of box numbers at the foot is the check.
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Congruent or Not? — Mystery Picture 25–35 minutes · 4 sheets
25 squares, each a pair of shapes drawn or described: fill the square if the two are congruent. Mirror images, a square turned into a diamond and an isosceles triangle on its side are congruent; an enlarged copy, two rectangles of one area and a near miss are not. When every square is right, an arrow appears.