Dilations: centre and scale factor
- The point that did not move — 3 tasks
- Count, do not measure — 3 tasks
- Building the image, one point at a time — 3 tasks
- Same triangle, same factor, new centre — 3 tasks
- Going Deeper — 9 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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Describe the Dilation Fully — Cut & Glue Sort 25 minutes · 5 sheets
12 pieces, each a drawing of a dilation with its center, two points and their images, and somebody’s description of it: sort them into correct, wrong (the factor upside down, the difference taken for the factor, a vertex named as the center) and not enough (the center or the factor left out).
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Dilations: Multiply, Never Add — Answer Maze 10–15 minutes · 4 sheets
One page, nothing to prepare: 8 boxes, each a dilation in words and one number asked — an image's distance, an original's, the scale factor, or a second point's image — with two answers: the right one, and the one you get by using the factor upside down or by adding where a dilation multiplies.
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Dilations: Is P′ the Image? — Mystery Picture 25–35 minutes · 4 sheets
25 squares, each a center O, a point P, a point P′ and a scale factor of 2, 3, ½ or ⅓: rule the ray from O through P, step the compass along it, and fill the square if P′ is the image — a point on the wrong side of O, with the factor upside down, a quarter off, or off the ray stays white.
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Dilations: Center and Scale Factor — Scavenger Hunt a full class period · 13 sheets
16 cards round the room: the image's distance from the center, the original's, the scale factor from two distances, a second point's image from one pair, and the factor when a point does not move — factors as fractions, decimals and a percent; a wrong answer lands on a card that sends the group back, and a clean run is 8 lines on the record sheet.