Let’s solve each problem step by step.
We are told to use the formula:
Circumference = 2 × π × r
and assume
π = 3.14
Remember:
- If you’re given the
diameter, divide it by 2 to get the radius (r).
- If you’re given the
radius, plug it directly into the formula.
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Problem 1: Diameter = 42 yd → Radius = 42 ÷ 2 = 21 yd
Circumference = 2 × 3.14 × 21 = 6.28 × 21
Calculate: 6 × 21 = 126, 0.28 × 21 = 5.88 → Total = 126 + 5.88 =
131.88 yd
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Problem 2: Diameter = 22 ft → Radius = 22 ÷ 2 = 11 ft
Circumference = 2 × 3.14 × 11 = 6.28 × 11
Calculate: 6 × 11 = 66, 0.28 × 11 = 3.08 → Total = 66 + 3.08 =
69.08 ft
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Problem 3: Radius = 17 in (given directly)
Circumference = 2 × 3.14 × 17 = 6.28 × 17
Calculate: 6 × 17 = 102, 0.28 × 17 = 4.76 → Total = 102 + 4.76 =
106.76 in
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Problem 4: Radius = 91 yd
Circumference = 2 × 3.14 × 91 = 6.28 × 91
Break it down: 6 × 91 = 546, 0.28 × 91 = let’s compute:
0.2 × 91 = 18.2, 0.08 × 91 = 7.28 → 18.2 + 7.28 = 25.48
Total = 546 + 25.48 =
571.48 yd
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Problem 5: Radius = 40 m
Circumference = 2 × 3.14 × 40 = 6.28 × 40
= 6 × 40 = 240, 0.28 × 40 = 11.2 → Total = 240 + 11.2 =
251.2 m
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Problem 6: Radius = 44 cm
Circumference = 2 × 3.14 × 44 = 6.28 × 44
6 × 44 = 264, 0.28 × 44 = 0.2×44=8.8, 0.08×44=3.52 → 8.8+3.52=12.32
Total = 264 + 12.32 =
276.32 cm
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Problem 7: Radius = 32 yd
Circumference = 2 × 3.14 × 32 = 6.28 × 32
6 × 32 = 192, 0.28 × 32 = 0.2×32=6.4, 0.08×32=2.56 → 6.4+2.56=8.96
Total = 192 + 8.96 =
200.96 yd
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Problem 8: Diameter = 12.5 ft → Radius = 12.5 ÷ 2 = 6.25 ft
Circumference = 2 × 3.14 × 6.25 = 6.28 × 6.25
Let’s compute: 6 × 6.25 = 37.5, 0.28 × 6.25
0.2 × 6.25 = 1.25, 0.08 × 6.25 = 0.5 → 1.25 + 0.5 = 1.75
Total = 37.5 + 1.75 =
39.25 ft
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Final Answer:
1. 131.88 yd
2. 69.08 ft
3. 106.76 in
4. 571.48 yd
5. 251.2 m
6. 276.32 cm
7. 200.96 yd
8. 39.25 ft
Parent Tip: Review the logic above to help your child master the concept of area and circumference of a circle worksheet answers.
