Similarity transformations; the definition of similar
- Four copies from a two-dial copier — 3 tasks
- Which way round, and with what numbers — 3 tasks
- Write the transformation, name every number — 3 tasks
- Accept one pair, refuse the other — 3 tasks
- Going Deeper — 3 tasks
- Practice — 20 tasks
- Summary — 2 tasks
- Cool-down — 6 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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Similar, or Which Part Fails? — Cut & Glue Sort 25 minutes, including the cutting · 5 sheets
12 pairs of shapes with their side lengths and angles, sorted into similar, not similar because no one number multiplies every side, and not similar although every side is multiplied by one number — a square and a rhombus, a rectangle and a parallelogram — while a congruent pair and a smaller copy wait in the first row.
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Similar or Not? Read the Numbers — Answer Maze 10–15 minutes · 4 sheets
8 boxes on one page, each a pair of shapes with their numbers: a congruent pair, a smaller copy, two rectangles whose angles match, a square and a rhombus with every side doubled, a triangle stretched one way. 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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Same Shape, Any Size? — Mystery Picture 25–35 minutes · 4 sheets
25 squares, each a pair of shapes drawn or described: fill the square if the two are similar. Congruent pairs, smaller copies, two squares and a dilation followed by a turn are similar; every side made 2 longer, a stretch one way and a square against a rhombus are not. When every square is right, a flag appears.