Practice Maths

Area of a Circle — Solutions

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  1. Find area given radius

    1. r=3 cm:
    2. r=7 m:
    3. r=5 mm:
    4. r=10 cm:
    5. r=2.5 m:
    6. r=12 cm:
    7. r=0.8 m:
    8. r=20 mm:

  2. Find area given diameter

    1. d=8 cm (r=4):
    2. d=14 m (r=7):
    3. d=6 mm (r=3):
    4. d=20 cm (r=10):
    5. d=3 m (r=1.5):
    6. d=9.4 cm (r=4.7):
    7. d=50 mm (r=25):
    8. d=1 m (r=0.5):

  3. Find radius from area

    1. A=50 cm²:
    2. A=78.54 m²:
    3. A=200 mm²:
    4. A=314 cm²:
    5. A=1 m²:
    6. A=100 cm²:
    7. A=400π mm²:
    8. A=9π cm²:

  4. Exact answers in terms of π

    1. r=4 cm:
    2. d=12 m (r=6):
    3. r=9 mm:
    4. d=1 cm (r=0.5):
    5. r=7 m:
    6. d=6 km (r=3):

  5. Compare areas

    1. Circle A (r=3) vs Circle B (r=6):
    2. Circumference 20 cm vs square perimeter 20 cm:
    3. Radius doubled:
    4. d=10 cm:

  6. Real-world area problems

    1. Pizzas d=30 and d=45:
    2. Pool A=50.27 m²:
    3. Circular coaster r=5 cm vs square side=9 cm:
    4. Garden r=4 m, $3.50/m²:

  7. Area from diagrams Understanding

  8. Area formula table Understanding

  9. Spot the error Understanding

  10. Extended response Problem Solving