To solve this worksheet, we need to calculate the
area of a circle for each problem using the formula:
>
A = π × r²
Where:
-
A is the area
-
π (pi) ≈ 3.14159 (we’ll use 3.1416 for calculation, then round final answer to
1 decimal place as instructed)
-
r is the
radius of the circle
⚠️
Important: Some problems give the
diameter (d), not the radius. Remember:
>
r = d ÷ 2
---
Let’s go through each problem one by one.
---
1) Diameter = 5 cm
→ Radius = 5 ÷ 2 =
2.5 cm
A = π × (2.5)² = 3.1416 × 6.25 ≈
19.635 → 19.6 cm²
✔ Answer: 19.6 cm²
---
2) Radius = 3 m
A = π × (3)² = 3.1416 × 9 ≈
28.274 → 28.3 m²
✔ Answer: 28.3 m²
---
3) Diameter = 8 mm
→ Radius = 8 ÷ 2 =
4 mm
A = π × (4)² = 3.1416 × 16 ≈
50.265 → 50.3 mm²
✔ Answer: 50.3 mm²
---
4) Radius = 1.5 m
A = π × (1.5)² = 3.1416 × 2.25 ≈
7.069 → 7.1 m²
✔ Answer: 7.1 m²
---
5) Diameter = 11 cm
→ Radius = 11 ÷ 2 =
5.5 cm
A = π × (5.5)² = 3.1416 × 30.25 ≈
95.033 → 95.0 cm²
✔ Answer: 95.0 cm²
---
6) Radius = 7 mm
A = π × (7)² = 3.1416 × 49 ≈
153.938 → 153.9 mm²
✔ Answer: 153.9 mm²
---
7) Diameter = 17 cm
→ Radius = 17 ÷ 2 =
8.5 cm
A = π × (8.5)² = 3.1416 × 72.25 ≈
226.980 → 227.0 cm²
✔ Answer: 227.0 cm²
---
8) Radius = 9 mm
A = π × (9)² = 3.1416 × 81 ≈
254.469 → 254.5 mm²
✔ Answer: 254.5 mm²
---
9) Diameter = 9 m
→ Radius = 9 ÷ 2 =
4.5 m
A = π × (4.5)² = 3.1416 × 20.25 ≈
63.617 → 63.6 m²
✔ Answer: 63.6 m²
---
10) Radius = 13 cm
A = π × (13)² = 3.1416 × 169 ≈
530.929 → 530.9 cm²
✔ Answer: 530.9 cm²
---
11) Diameter = 15 mm
→ Radius = 15 ÷ 2 =
7.5 mm
A = π × (7.5)² = 3.1416 × 56.25 ≈
176.715 → 176.7 mm²
✔ Answer: 176.7 mm²
---
12) Radius = 6½ cm = 6.5 cm
A = π × (6.5)² = 3.1416 × 42.25 ≈
132.732 → 132.7 cm²
✔ Answer: 132.7 cm²
---
##
✔ Final Answers (to 1 decimal place):
1)
19.6 cm²
2)
28.3 m²
3)
50.3 mm²
4)
7.1 m²
5)
95.0 cm²
6)
153.9 mm²
7)
227.0 cm²
8)
254.5 mm²
9)
63.6 m²
10)
530.9 cm²
11)
176.7 mm²
12)
132.7 cm²
---
📌
Tip for students: Always check if the given measurement is
radius or diameter. If it’s diameter, divide by 2 first! Then plug into A = πr² and round to 1 decimal place.
Let me know if you want a printable version or step-by-step working for any specific problem!
Parent Tip: Review the logic above to help your child master the concept of area of circle worksheet.
