Let’s solve each circle area problem step by step.
We’ll use the formula for the area of a circle:
Area = π × r²
where
r is the radius (half the diameter).
We’re told to round answers to 3 decimal places and use
π ≈ 3.14159.
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Problem ①: Radius = 2 ft
Area = π × (2)² = 3.14159 × 4 =
12.56636 → Round to 3 decimals →
12.566 ft²
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Problem ②: Diameter = 10 m → Radius = 10 ÷ 2 = 5 m
Area = π × (5)² = 3.14159 × 25 =
78.53975 → Round to 3 decimals →
78.540 m²
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Problem ③: Diameter = 8 cm → Radius = 8 ÷ 2 = 4 cm
Area = π × (4)² = 3.14159 × 16 =
50.26544 → Round to 3 decimals →
50.265 cm²
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Problem ④: Radius = 3 in
Area = π × (3)² = 3.14159 × 9 =
28.27431 → Round to 3 decimals →
28.274 in²
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Problem ⑤: Radius = 4 yd
Area = π × (4)² = 3.14159 × 16 =
50.26544 → Round to 3 decimals →
50.265 yd²
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Problem ⑥: Diameter = 12 mm → Radius = 12 ÷ 2 = 6 mm
Area = π × (6)² = 3.14159 × 36 =
113.09724 → Round to 3 decimals →
113.097 mm²
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Problem ⑦: Diameter = 10 km → Radius = 10 ÷ 2 = 5 km
Area = π × (5)² = 3.14159 × 25 =
78.53975 → Round to 3 decimals →
78.540 km²
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Problem ⑧: Radius = 2 mi
Area = π × (2)² = 3.14159 × 4 =
12.56636 → Round to 3 decimals →
12.566 mi²
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Problem ⑨: Diameter = 6 ft → Radius = 6 ÷ 2 = 3 ft
Area = π × (3)² = 3.14159 × 9 =
28.27431 → Round to 3 decimals →
28.274 ft²
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Final Answer:
① 12.566 ft²
② 78.540 m²
③ 50.265 cm²
④ 28.274 in²
⑤ 50.265 yd²
⑥ 113.097 mm²
⑦ 78.540 km²
⑧ 12.566 mi²
⑨ 28.274 ft²
Parent Tip: Review the logic above to help your child master the concept of circle area worksheet answers.
