Circle vocabulary; all circles are similar
- Building the circle out of six dots — 3 tasks
- Saying the length before drawing the segment — 3 tasks
- Naming the parts of a circle — 3 tasks
- All circles are similar — 3 tasks
- Going Deeper — 4 tasks
- Practice — 28 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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Radius, Chord, or No Name? Circle Vocabulary — Cut & Glue Sort 25 minutes, including the cutting · 5 sheets
12 circles, each with its center dotted and one thick segment. Students sort each piece by where the segment's two ends are: a radius, a chord (diameters included), or a segment that has no name at all, such as one that runs from the circle to a point outside it.
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All Circles Are Similar: Find the Scale Factor — Radius or Diameter? — Answer Maze 10–15 minutes · 4 sheets
8 boxes on one page, each two circles drawn to scale with a radius or a diameter marked on each. Students translate one circle onto the other and find the scale factor of the dilation, the ratio of the radii in the right order. The wrong answers are the two commonest mistakes: the factor turned upside down, and a diameter used as a radius. The row of box numbers at the foot is the check.
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Is It a Chord? Circle Vocabulary: Radius, Chord, Diameter, Secant, Tangent, Arc — Mystery Picture 25–35 minutes · 5 sheets
25 squares, each a circle with one thick part: a chord, a diameter, a radius, a secant line, a tangent line, an arc, or a segment with no name. Students decide one thing for each: is the thick part a chord? Fill it or leave it white, and a picture appears. No numbers and no arithmetic.
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All Circles Are Similar: Find the Scale Factor — Radius or Diameter? — Scavenger Hunt a full class period · 13 sheets
16 cards around the room, each two circles drawn to scale with one radius or diameter marked on each. Students translate one circle onto the other and find the scale factor of the dilation: the ratio of the radii, in the right order. Turning the factor upside down, or using a diameter as a radius, lands on a card that sends the group back, and a clean run is 8 lines on the record sheet.