Surface Areas & Volumes | Exercise 13.4 | Q8

Question 8: A hemispherical bowl is made of steel, 0.25 cm thick. The inner radius of the bowl is 5 cm. Find the outer curved surface area of the bowl.

Video Explanation

Explanatory Answer | Exercise 13.4 Question 8

Given Data:
1. Thickness of the hemispherical bowl = 0.25 cm
2. Inner radius of the bowl, r₁ = 5 cm

∴ outer radius of the hemispherical bowl, r₂ = Inner radius + Thickness
= 5 + 0.25
= 5.25 cm = \\frac{10.5}{2}) = \\frac{21}{4})

Outer curved surface area of hemisphere = 2 × π × r₂²
Take π = \\frac{22}{7})
Outer curved surface area of hemisphere = 2 × \\frac{22}{7}) × \\frac{21}{4}) × \\frac{21}{4})
= 2 × 22 × \\frac{3}{4}) × \\frac{21}{4})
= 11 × 3 × \\frac{21}{4})
= \\frac{693}{4}) = 173.25

Outer curved surface area of hemispherical bowl = 173.25 cm²

Exercise 13.1 | Surface Area of Cubes & Cuboids

1. Class 9 Exercise 13.1 Question 3 | Height of hall ▶
2. Class 9 Exercise 13.1 Question 6 | TSA of Herbarium ▶
3. Class 9 Exercise 13.1 Question 7 | Shanti Sweets ▶

Exercise 13.2 | Surface Area of Cylinders

1. Class 9 Exercise 13.2 Question 3 | CSA TSA of Metal Pipe ▶
2. Class 9 Exercise 13.2 Question 4 | Roller & Playground ▶
3. Class 9 Exercise 13.2 Question 9 | Cylindrical Petrol Tank ▶
4. Class 9 Exercise 13.2 Question 10 | CSA of Decorative Lampshade ▶

Exercise 13.3 | Surface Area of Cones

1. Class 9 Exercise 13.3 Question 5 | Length of Tarpaulin 3 m wide ▶
2. Class 9 Exercise 13.3 Question 8 | Cost of painting conical barricades ▶

Exercise 13.4 | Surface Area of Spheres & Hemispheres

1. Class 9 Exercise 13.4 Question 8 | Outer CSA of hemispherical bowl ▶
2. Class 9 Exercise 13.4 Question 9 | Surface area of sphere & Cylinder ▶