# NCERT Solutions For Class 9 Maths Chapter 13 Surface Areas and Volumes Ex 13.8

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Textbook | NCERT |

Board | CBSE |

Category | NCERT Solutions |

Class | Class 9 |

Subject | Maths |

Chapter | Chapter 13 |

Exercise | Class 9 Chapter 13 Surface Areas and Volumes Exercise 13.8 |

Number of Questions Solved | 10 |

## NCERT Solutions for Class 9 Maths Chapter 13 Surface Areas and Volumes Ex 13.8

**NCERT TEXTBOOK EXERCISES**

**Question 1. Find the volume of a sphere whose radius is**

**(i) 7 cm****(ii) 0.63 cm**

**Solution:**

(i) We have, r = 7 cm

**Question 2. Find the amount of water displaced by a solid spherical ball of diameter**

**(i) 28 cm****(ii) 0.21 m**

**Solution:**

(i) We have, d = 28 cm

â‡’ r = 14 cm

**Question 3. The diameter of a metallic ball is 4.2 cm. What is the mass of the ball, if the density of the metal is 8.9 g per cm ^{3}?**

**Solution:**

We have, d = 4.2 cm â‡’ r = 2.1 cm

The density of the metal per cm^{3} = 8.9 g

The density of the metal 38.808 cm^{3} = 38.808 x 8.9 g = 345.39 g

Hence, the mass of the ball = 345.39 g

**Question 4. The diameter of the Moon is approximately one-fourth of the diameter of the Earth. What fraction of the volume of the Earth is the volume of the Moon?**

**Solution:**

Let diameter of the Earth is d_{3}.

We have, diameter of Moon (d_{1}) = 14 diameter of the Earth

**Question 5. How many litres of milk can a hemispherical bowl of diameter 10.5 cm hold?**

**Solution:**

Diameter = 10.5 cm

â‡’ Radius, r = 5.25 cm

**Question 6. A hemispherical tank is made up of an iron sheet 1 cm thick. If the inner radius is 1 m, then find the volume of the iron used to make the tank.**

**Solution:**

Inner radius (r_{1}) = 1 m -100 cm

Outer radius (r_{2}) = (100 + 1)cm ( âˆµ Inner radius + Thickness)

= 101 cm

**Question 7. Find the volume of a sphere whose surface area is 154 cm ^{2}.**

**Solution:**

We have, surface area of a sphere = 154 cm^{2}

**Question 8. A dome of a building is in the form of a hemisphere. From inside, it was white washed at the cost of â‚¹498.96. If the cost of white washing is â‚¹2.00 per square metre, find the**

**(i) inside surface area of the dome,****(ii) volume of the air inside the dome.**

**Solution:**

Cost of white washed = â‚¹ 498.96

Cost of white washing per square metre = â‚¹ 2.00

**Question 9. Twenty seven solid iron spheres, each of radius r and surface area S are melted to form a sphere with surface area Sâ€™. Find the**

**(i) radius râ€™ of the new sphere,****(ii) ratio of S and Sâ€™.**

**Solution:**

**Question 10. A capsule of medicine is in the shape of a sphere of diameter 3.5 mm. How much medicine (in mm ^{3}) is needed to fill this capsule?**

**Solution:**

We have, diameter = 3.5 mm

## NCERT Solutions for Class 9 Maths Chapter 13 Surface Areas and Volumes Exercise 13.8 PDF

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### Other Chapter of Class 9 Maths Chapter 13 Surface Areas and Volumes

**Surface Areas and Volumes Class 9 Ex 13.1****Surface Areas and Volumes Class 9 Ex 13.2****Surface Areas and Volumes Class 9 Ex 13.3****Surface Areas and Volumes Class 9 Ex 13.4****Surface Areas and Volumes Class 9 Ex 13.5****Surface Areas and Volumes Class 9 Ex 13.6****Surface Areas and Volumes Class 9 Ex 13.7****Surface Areas and Volumes Class 9 Ex 13.8****Surface Areas and Volumes Class 9 Ex 13.9**