Surface Areas & Volumes | Exercise 13.3 | Q7

Question 7: A joker’s cap is in the form of a right circular cone of base radius 7 cm and height 24 cm. Find the area of the sheet required to make 10 such caps.

Explanatory Answer | Exercise 13.3 Question 7

Given Data: Radius of the conical cap, r = 7 cm
Height of the conical cap, h = 24 cm

Step 1: Compute slant height of the cone

Square of slant height of the cone, l² = h² + r²
= 24² + 7²
= 576 + 49 = 625
Or slant height, l = 25 cm

Step 2: Compute Curved Surface Area of Cone

Curved surface area of one conical cap = π × r × l
Take π = \\frac{22}{7})
= \\frac{22}{7}) × 7 × 25
= 22 × 25
= 550 cm²

Step 3: Compute Area of Sheet Required for 10 Caps

Area of sheet required to make 10 conical caps = 550 × 10
= 5500 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 ▶