3.1 Circles

• Circumference of a circle
• Length of an arc of a circle
• Perimeter of a sector of a circle

• work out the circumference of a circle in real-life situations
• work out the length of an arc of a circle in different situations
• calculate the perimeter of a sector of a circle in different situations
• promote use of circles in real-life situations

“How do we determine the circumference of a circle?”

“How do we use sectors of a circle in real-life situations?”

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1. The circumference of a circle
   40 min · 1 practice tasks · quiz
   Why every circle has a circumference just over three diameters long, and the two formulas that follow.
2. Working backwards from the circumference
   40 min · 1 practice tasks · quiz
   Finding a diameter or radius from a known circumference, and using circumference to work out how far a wheel travels.
3. The length of an arc
   40 min · 1 practice tasks · quiz
   An arc as a fraction of the circumference, found from the angle at the centre.
4. The perimeter of a sector
   40 min · 1 practice tasks · quiz
   Adding the arc and the two radii, and remembering that a boundary must go all the way round.
5. Circles and sectors in real life
   40 min · 1 practice tasks · quiz
   Where circumference and sectors are actually used, and making a cone from a sector.