Dilating lines, segments and angles
- The same mark at two sizes — 3 tasks
- One image line — 3 tasks
- Does the centre lie on the line? — 3 tasks
- What the factor multiplies — 3 tasks
- What is proved, and what is owed — 9 tasks
- Practice — 23 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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Dilations: Always, Sometimes or Never? — Cut & Glue Sort 25 minutes · 5 sheets
12 sentences about what a dilation does to a line, a segment, an angle or its center: sort them into always true, sometimes true (it depends on whether the center is on the line) and never true (the angle multiplied by the factor, the segment the same length, the center moving).
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Dilations: Lengths Grow, Angles Stay — Answer Maze 10–15 minutes · 4 sheets
One page, nothing to prepare: 8 boxes, each a dilation in words — an image segment's length, an image angle's measure, or whether a line's image is the line itself or a parallel line — with two answers: the right one, and the one you get by multiplying the angle, keeping the length, or mixing up "same line" and "parallel line".
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Dilations: Is Line AB Its Own Image? — Mystery Picture 20–30 minutes · 4 sheets
25 squares, each a triangle ABC and a center O: lay a ruler on A and B, and fill the square if line AB passes through O, so that the dilation takes line AB to itself — O inside the triangle, on another side’s line, or a little off line AB stays white.
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Dilating Segments and Angles — Scavenger Hunt a full class period · 13 sheets
16 cards round the room: a segment's image length, the original length, the scale factor from two lengths, a second segment from one pair, and the measure of an image angle — some printed beside arms that grow; a wrong answer lands on a card that sends the group back, and a clean run is 8 lines on the record sheet.