Let’s solve each problem step by step.
We are told to use π = 3.14
The formula for the area of a circle is:
Area = π × r²
where
r is the radius.
But sometimes we’re given the
diameter, not the radius.
Remember:
radius = diameter ÷ 2
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Problem 1: Diameter = 18 cm → Radius = 18 ÷ 2 = 9 cm
Area = 3.14 × 9² = 3.14 × 81 =
254.34 cm²
Problem 2: Diameter = 8 m → Radius = 8 ÷ 2 = 4 m
Area = 3.14 × 4² = 3.14 × 16 =
50.24 m²
Problem 3: Diameter = 36 ft → Radius = 36 ÷ 2 = 18 ft
Area = 3.14 × 18² = 3.14 × 324 =
1017.36 ft²
Problem 4: Diameter = 52 m → Radius = 52 ÷ 2 = 26 m
Area = 3.14 × 26² = 3.14 × 676 =
2122.64 m²
Problem 5: Radius = 19 mm (already given)
Area = 3.14 × 19² = 3.14 × 361 =
1133.54 mm²
Problem 6: Radius = 31 ft (already given)
Area = 3.14 × 31² = 3.14 × 961 =
3017.54 ft²
Problem 7: Diameter = 78 m → Radius = 78 ÷ 2 = 39 m
Area = 3.14 × 39² = 3.14 × 1521 =
4775.94 m²
Problem 8: Radius = 21 ft (already given)
Area = 3.14 × 21² = 3.14 × 441 =
1384.74 ft²
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Final Answer:
1. 254.34 cm²
2. 50.24 m²
3. 1017.36 ft²
4. 2122.64 m²
5. 1133.54 mm²
6. 3017.54 ft²
7. 4775.94 m²
8. 1384.74 ft²
Parent Tip: Review the logic above to help your child master the concept of find the area of a circle worksheet.
