Question

CHECKING YOUR UNDERSTANDING

Choose the letter of the best answer. Write the chosen letter on a separate sheet of
paper
1. A dinner plate has a diameter of 10.2 cm. What is the area of the dinner plate?
A. 81.67 cm
C. 93.84 cm
B. 85.12 cm
D. 100.02 cm
2. A dog is tied to a wooden stake in a yard. His leash is 3 m long, and he runs around
in circles pulling the leash as far as it can go. How much area does the dog have
to run around ?
A. 26.28 m2
C. 29.66 m2
B. 28.26 m2
D. 32.28 m²
3. A storm is expected to hit 7 mi in every direction from a small town of Malabon.
What is the area that the storm will affect?
A. 116.68 mi
C. 150.67 mi
B. 124.83 mi
D. 153.86 mi
4. Every December, an amusement park is constructed in Malabon Robinsons Town
mall. A carousel is the most favorite ride of the kids there. The diameter of the
carousel is 20.5 m. What is the area of the carousel?
A. 329.90 m²
C. 392.90 m2
B. 328.90 m2
D. 391.90 m2
5. A lawn sprinkler sprays water 4.5 ft in every direction as it rotates. What is the area
of the sprinkled lawn?
A. 56.885 ft
C. 63.585 ft
B. 60.855 ft
D. 65.385 ft ​

Answer 1

1) 81.67 cm² (Option A)

2) 28.26 m² (Option B)

3) 153.86 mi.² (Option D)

4) 329.90 m² (Option A)

5) 63.585 ft.² (Option C)

Explanation:

GENERAL FORMULAES TO BE USED IN THIS QUESTION :-

Diameter of a circle with radius 'r' = 2r

Area of a circle with radius 'r' = πr²

SOLUTION :-

1) Diameter of the dinner plate = 10.2 cm

Radius of the dinner plate = 10.2/2 = 5.1 cm

⇒ Area of the circle = π(5.1)² = 26.01π cm² ≈ 81.67 cm²

2) Length of his leash = 3m

⇒ Area the dog has to run around = π(3)² = 9π m² = 28.26 m²

3) Radius of the circular range of storm = 7 mi.

⇒ Area of the circular range of storm = π(7)² = 49π mi.² = 153.86 mi.²

4) Diameter of carousel = 20.5 m

Radius of carousel = 20.5/2 = 10.25 m

⇒ Area of the carousel = π(10.25)² = 105.0625π m² ≈ 329.90 m²

5) Radius of the range of sprinkler = 4.5 ft.

⇒ Area of the range of sprinkler = π(4.5)² = 20.25π ft.² = 63.585 ft.²