Starter quiz
- Round 50.26548246 to 1 decimal place.
- '50.3' ✓
- Round 3.14159265 to 3 significant figures.
- '3.14' ✓
The perimeter of the parallelogram is ______ units.- 8
- 12
- 16 ✓
- 24
-
- Select the rectangle with the largest perimeter.
- . Find the value of when .
- '18' ✓
- . Find the value of when .
- '2' ✓
Exit quiz
Which part of the circle is labelled?- arc
- circumference
- diameter
- radius ✓
-
- The ______ of a circle is the perimeter of the circle.
- 'circumference' ✓
- If a circle has a radius of 12 cm then its diameter will be ______ cm.
- '24' ✓
- Which symbol represents the ratio between the diameter and circumference of a circle?
-
-
-
- ✓
-
- Which are the first three digits of ?
- '3.14' ✓
- A circle with diameter 10 cm has a circumference of ______ cm.
- 5
- 10 ✓
- 20
-
Worksheet
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Presentation
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Lesson Details
Key learning points
- There is a multiplicative relationship between the radius and diameter of a circle.
- The ratio between the diameter and circumference of a circle is always the same.
- That ratio is called π and it is an irrational number.
- The formula for the circumference of a circle is C = πd.
- Using the definition of the diameter you can also write this as C = 2πr.
Common misconception
Pupils may think that the π symbol represents a variable, similar to letters such as r and d.
Reiterate the difference between variables and constants. Explain that while the radius may differ between circles, π is always the same.
Keywords
Diameter - The diameter of a circle is any line segment that starts and ends on the edge of the circle and passes through the centre.
Radius - The radius of a circle is any line segment that joins the centre of a circle to its edge.
Circumference - The circumference of a circle is the perimeter of the circle.
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