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(b) If the diameter of the base of a cylindrical pipe is 30 cm, find the area of the base of the pipe. [tex](\pi=3.14)[/tex]

7. (a) If the area of the base of a cylindrical tank is 154 sq. ft, find the radius and the circumference of it. [tex](\pi= \frac{22}{7})[/tex]

(b) A circular playground of area [tex]153.86 m^2[/tex] is plastered. What is the diameter of the plastered part of the playground? Also, find its circumference. [tex](\pi=3.14)[/tex]


Sagot :

Sure, let's break it down step by step.

### (b) If the diameter of the base of a cylindrical pipe is 30 cm, find the area of the base of the pipe. [tex]\((\pi=3.14)\)[/tex]

1. Given:
- Diameter of the base of the cylindrical pipe, [tex]\(d = 30\)[/tex] cm

2. Calculate the radius:
[tex]\[ r = \frac{d}{2} = \frac{30}{2} = 15 \text{ cm} \][/tex]

3. Calculate the area of the base:
[tex]\[ \text{Area of the base} = \pi r^2 = 3.14 \times (15)^2 \][/tex]
[tex]\[ \text{Area of the base} = 3.14 \times 225 = 706.5 \text{ cm}^2 \][/tex]

Therefore, the area of the base of the cylindrical pipe is [tex]\(706.5 \text{ cm}^2\)[/tex].

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### 7. (a) If the area of the base of a cylindrical tank is 154 sq. ft, find the radius and the circumference of it. [tex]\((\pi=22 / 7)\)[/tex]

1. Given:
- Area of the base of the cylindrical tank, [tex]\(A = 154\)[/tex] sq. ft

2. Calculate the radius:
[tex]\[ A = \pi r^2 \][/tex]
[tex]\[ 154 = \frac{22}{7} r^2 \][/tex]
[tex]\[ 154 = \frac{22}{7} r^2 \][/tex]
[tex]\[ \Rightarrow r^2 = \frac{154 \times 7}{22} = 49 \][/tex]
[tex]\[ \Rightarrow r = \sqrt{49} = 7 \text{ ft} \][/tex]

Therefore, the radius of the base of the cylindrical tank is 7 ft.

3. Calculate the circumference:
[tex]\[ C = 2\pi r \][/tex]
[tex]\[ C = 2 \times \frac{22}{7} \times 7 \][/tex]
[tex]\[ C = 2 \times 22 = 44 \text{ ft} \][/tex]

Therefore, the circumference of the base of the cylindrical tank is 44 ft.

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### 7. (b) A circular playground of area [tex]\(153.86\, m^2\)[/tex] is plastered. What is the diameter of the plastered part of the playground? Also, find its circumference. [tex]\((\pi=3.14)\)[/tex]

1. Given:
- Area of the circular playground, [tex]\(A = 153.86 \text{ m}^2\)[/tex]

2. Calculate the radius:
[tex]\[ A = \pi r^2 \][/tex]
[tex]\[ 153.86 = 3.14 r^2 \][/tex]
[tex]\[ r^2 = \frac{153.86}{3.14} = 49 \][/tex]
[tex]\[ r = \sqrt{49} = 7 \text{ m} \][/tex]

Therefore, the radius of the circular playground is 7 m.

3. Calculate the diameter:
[tex]\[ d = 2r = 2 \times 7 = 14 \text{ m} \][/tex]

Therefore, the diameter of the plastered part of the playground is 14 m.

4. Calculate the circumference:
[tex]\[ C = 2\pi r \][/tex]
[tex]\[ C = 2 \times 3.14 \times 7 = 43.96 \text{ m} \][/tex]

Therefore, the circumference of the plastered part of the playground is 43.96 m.

In summary:
- The area of the base of the cylindrical pipe is [tex]\(706.5 \text{ cm}^2\)[/tex].
- The radius and circumference of the cylindrical tank are 7 ft and 44 ft, respectively.
- The diameter and circumference of the plastered part of the playground are 14 m and 43.96 m, respectively.
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