Practise circumference, area, chords and tangents with simple circle diagrams.
Example 1
A circle has diameter 6cm. Find its radius, in cm.
CircleDiagram not to scaleShow worked answer
Answer: 3
- The radius is half the diameter: 26=3cm.
Example 2
A circle has radius 7cm. Its circumference is kπcm. Find k.
CircleDiagram not to scaleShow worked answer
Answer: 14
- Circumference =2πr=2×π×7=14πcm.
- The coefficient k is 14.
Example 3
A circle has diameter 20cm. Its area is kπcm2. Find k.
CircleDiagram not to scaleShow worked answer
Answer: 100
- The radius is 220=10cm.
- Area =πr2=π×102=100πcm2, so k=100.