Rigid and non-rigid: what is preserved
- Two correct measurements, two different verdicts — 3 tasks
- The row nobody thought to fill — 3 tasks
- An image that agrees and still looks wrong — 3 tasks
- What a rigid motion keeps, and what it does not — 6 tasks
- Sorting eight transformations — 4 tasks
- Practice — 22 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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Rigid and Non-Rigid — Cut & Glue Sort 25 minutes, including the cutting · 5 sheets
12 statements about a rule, sorted into a rigid motion, not rigid and cannot tell — where one segment that kept its length settles nothing, the same area settles nothing, a mirror image is still rigid, and one distance that changed settles it.
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Rigid and Non-Rigid — Answer Maze 10–15 minutes · 4 sheets
One page and nothing to prepare: 8 boxes about what a rigid motion keeps — one segment that agrees, the same area, a mirror image, a slide of 100 squares — where a wrong answer is either “what I measured agreed, so it is rigid” or “it looks changed, so it is not”, and leads to a box that sends you back.
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Rigid and Non-Rigid — Mystery Picture 20–30 minutes · 4 sheets
25 figures and their images on squared paper, no numbers: fill the square if some side or some corner changed, and leave it white if everything agrees — where a stretch keeps one side, a shear keeps the area, and a mirror image is still rigid.
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Rigid and Non-Rigid — Scavenger Hunt a full class period · 13 sheets
16 cards round the room, each a stretch in one direction and two points: how far apart are their images? Half the lengths change and half do not — a wrong answer lands on a card that sends the group back, and a clean run is 8 lines on the record sheet.