Surface Areas & Volumes | Exercise 13.4 | Q6

Question 6: Find the radius of a sphere whose surface area is 154 cm².

Explanatory Answer | Exrecise 13.4 Question 6

Surface area of sphere = 154 cm²
Let r be the radius of the sphere.
Surface area of sphere = 4 × π × r²
Take π = \\frac{22}{7})
154 = 4 x \\frac{22}{7}) x r²
r² = 154 x \\frac{7}{22 \times 4})
r² = \\frac{7}{2}) x \\frac{7}{2})
Take square root on both sides: r = \\frac{7}{2})
Radius of the sphere = 3.5 cm

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 ▶