BUILD FLUENCY. EARN YOUR ASCENT.Sign in Year 10
Annuli, sectors and area constraints
Free examples and worked answers. No account needed.
Practise the method.
Annuli, sectors and area constraints
Annuli, sectors and area constraints
Example 1
A circular ring has area 72cm2 and width 2cm. Find its outer radius x. Use π=3.
AnnulusDiagram not to scaleShow worked answer
Answer: 7
- Its inner radius is x−2.
- Solve 3[x2−(x−2)2]=72;
- x=7cm.
Example 2
A sector has radius 12cm and central angle 150∘. Find its area in cm2. Use π=3.
Circular sectorDiagram not to scaleShow worked answer
Answer: 180
- Sector area =(360150)×3×122=180cm2.
Example 3
A circular ring has area 36cm2 and width 2cm. Find its outer radius x. Use π=3.
AnnulusDiagram not to scaleShow worked answer
Answer: 4
- Its inner radius is x−2.
- Solve 3[x2−(x−2)2]=36;
- x=4cm.
Put it into practice.
Sign in to choose a set, get feedback and keep your progress.