Perimeter, area and volume · Ages 11–12

Area of a circle worksheet

Part of: Circumference and area of a circle

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Perimeter, area and volume · Ages 11–12

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Write each answer in the space. For word problems, show your working and write a sentence answer.

1.Find the area of this circle. (Take π as 3.14.) The answer is cm²
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2.Find the area of this circle. (Take π as 3.14.) The answer is cm²
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3.Take π as 3.14. A circle's circumference is 75.36 cm. What is its area, in cm²?
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4.Take π as 227. What is the area of a circle of radius 14 cm, in cm²?
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5.Take π as 3.14. A circle's circumference is 50.24 cm. What is its area, in cm²?
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6.Take π as 227. What is the area of a circle of radius 42 cm, in cm²?
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7.Take π as 3.14. A circle's circumference is 69.08 cm. What is its area, in cm²?
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8.A circle 6 cm across has an area of 113.04 cm². (Take π as 3.14.)
True or false?
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9.Take π as 3.14. What is the area of a circle of radius 7 cm, in cm²?
- A. 153.86
- B. 21.98
- C. 615.44
- D. 43.96
Choose the right answer
Answer:
10.Take π as 3.14. What is the area of a circle of radius 5 cm, in cm²?
- A. 314
- B. 15.7
- C. 31.4
- D. 78.5
Choose the right answer
Answer:
11.A circle 18 cm across has an area of 254.34 cm². (Take π as 3.14.)
True or false?
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12.Take π as 3.14. What is the area of a circle of radius 11 cm, in cm²?
- A. 379.94
- B. 69.08
- C. 1519.76
- D. 34.54
Choose the right answer
Answer:

13.Take π as 3.14. Ka-yee's grandpa has a round flower bed of radius 2 m, and each square metre needs 50 g of plant food. How many grams does the whole bed need?
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14.Take π as 3.14. A large pizza is 36 cm across and a small one 18 cm. How many cm² bigger is one large pizza than two small ones together?
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15.Take π as 3.14. Tsz-hin walks once round a round swimming pool and finds the edge is 69.08 m long. What is the area of the water's surface, in m²?
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16.Take π as 3.14. A sprinkler in the middle of a lawn turns all the way round, and its water reaches 8 m at most. What area can it water, in m²?
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17.Take π as 3.14. A sprinkler in the middle of a lawn turns all the way round, and its water reaches 11 m at most. What area can it water, in m²?
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18.Take π as 3.14. Ka-lok's grandpa has a round flower bed of radius 2 m, and each square metre needs 10 g of plant food. How many grams does the whole bed need?
Working:
Answer:

Show the answers and working

Area of a circle worksheet: Answers and working

1. 3.14
The 1 cm in the picture is the radius. Area = 3.14 × r × r, so work out 1 × 1 first.
1 × 1 = 1; 3.14 × 1 = 3.14.
2. 113.04
The picture gives the diameter, 12 cm. Find the radius first: 12 ÷ 2.
The picture gives the diameter, so the radius is 12 ÷ 2 = 6; 3.14 × 6 × 6 = 113.04.
3. 452.16 cm²
The area needs the radius. Find the diameter from the circumference, 75.36 ÷ 3.14, then the radius.
Diameter = 75.36 ÷ 3.14 = 24, so the radius is 12; 3.14 × 12 × 12 = 452.16.
4. 616 cm²
Area = 227 × 14 × 14. 14 is a multiple of 7, so cancel the 7 first.
227 × 14 × 14: cancel the 7 first, 22 × 2 × 14 = 616.
5. 200.96 cm²
The area needs the radius. Find the diameter from the circumference, 50.24 ÷ 3.14, then the radius.
Diameter = 50.24 ÷ 3.14 = 16, so the radius is 8; 3.14 × 8 × 8 = 200.96.
6. 5544 cm²
Area = 227 × 42 × 42. 42 is a multiple of 7, so cancel the 7 first.
227 × 42 × 42: cancel the 7 first, 22 × 6 × 42 = 5544.
7. 379.94 cm²
The area needs the radius. Find the diameter from the circumference, 69.08 ÷ 3.14, then the radius.
Diameter = 69.08 ÷ 3.14 = 22, so the radius is 11; 3.14 × 11 × 11 = 379.94.

8. False
6 cm is the diameter, but the area needs the radius. Find it, work out the area and compare with 113.04.
Find the radius first, 6 ÷ 2 = 3: 3.14 × 3 × 3 = 28.26.
9. A. 153.86
Area is 3.14 × r × r, the radius twice. Work out 7 × 7 first.
3.14 × 7 × 7 = 153.86.
10. D. 78.5
Area is 3.14 × r × r, the radius twice. Work out 5 × 5 first.
3.14 × 5 × 5 = 78.5.
11. True
18 cm is the diameter, but the area needs the radius. Find it, work out the area and compare with 254.34.
Find the radius first, 18 ÷ 2 = 9: 3.14 × 9 × 9 = 254.34.
12. A. 379.94
Area is 3.14 × r × r, the radius twice. Work out 11 × 11 first.
3.14 × 11 × 11 = 379.94.

Marking: 2 for the working, 1 for the answer, 1 for the sentence.

13. 628 g
Find the bed's area first, 3.14 × 2 × 2, then think about 50 g a square metre.
Area: 3.14 × 2 × 2 = 12.56 m²; 12.56 × 50 = 628 g.
14. 508.68 cm²
Find both radii first, 36 ÷ 2 and 18 ÷ 2, then each area.
Small: 3.14 × 9 × 9 = 254.34; large: twice the radius, 4 times the area, 1017.36; 1017.36 − 2 × 254.34 = 508.68.
15. 379.94 m²
The edge is the circumference. Find the diameter from 69.08 ÷ 3.14, then the radius.
The edge is the circumference: diameter = 69.08 ÷ 3.14 = 22, radius 11; 3.14 × 11 × 11 = 379.94.
16. 200.96 m²
The watered area is a circle with radius 8 m. Area = 3.14 × r × r.
It waters a circle of radius 8 m: 3.14 × 8 × 8 = 200.96.
17. 379.94 m²
The watered area is a circle with radius 11 m. Area = 3.14 × r × r.
It waters a circle of radius 11 m: 3.14 × 11 × 11 = 379.94.
18. 125.6 g
Find the bed's area first, 3.14 × 2 × 2, then think about 10 g a square metre.
Area: 3.14 × 2 × 2 = 12.56 m²; 12.56 × 10 = 125.6 g.

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