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13. Surface Areas and Volumes Mathematics class 9 in English Medium ncert book solutions Exercise 13.4
13. Surface Areas and Volumes Exercise 13.4 – Complete NCERT Book Solutions for Class 9 Mathematics (English Medium). Get all chapter explanations, extra questions, solved examples and additional practice questions for 13. Surface Areas and Volumes Exercise 13.4 to help you master concepts and score higher.
13. Surface Areas and Volumes Mathematics class 9 in English Medium ncert book solutions Exercise 13.4
NCERT Solutions for Class 9 Mathematics play an important role in helping students understand the concepts of the chapter 13. Surface Areas and Volumes clearly. This chapter includes the topic Exercise 13.4, which is essential from both academic and examination point of view. The solutions provided here are prepared strictly according to the latest NCERT syllabus and follow the guidelines of CBSE to ensure accuracy and relevance. Each question is explained in a simple and student-friendly manner so that learners can grasp the concepts without confusion. These NCERT Solutions are useful for regular study, homework help, and exam preparation. All textbook questions are solved step by step to improve problem-solving skills and conceptual clarity. Students of Class 9 studying Mathematics can use these solutions to revise important topics, understand difficult questions, and practise effectively before examinations. The chapter 13. Surface Areas and Volumes is explained in a structured way, making it easier for students to connect the theory with the topic Exercise 13.4. By studying these updated NCERT Solutions for Class 9 Mathematics, students can build a strong foundation, boost their confidence, and score better marks in school and board exams.
13. Surface Areas and Volumes
Exercise 13.4
Exercise 13.4
Assume π = 22/7 , unless stated otherwise.
Q1. Find the surface area of a sphere of radius:
(i) 10.5 cm (ii) 5.6 cm (iii) 14 cm
Solution:
Q2. Find the surface area of a sphere of diameter:
(i) 14 cm (ii) 21 cm (iii) 3.5 m
Solution:
(i) Surface area of sphere = 4πr2
Q3. Find the total surface area of a hemisphere of radius 10 cm. (Use π = 3.14)
Solution:
Total surface area of hemisphere = 3πr2
⇒ 3 × 3.14 × 10 × 10
⇒ 3 × 314
⇒ 942 cm2
Q4. The radius of a spherical balloon increases from 7 cm to 14 cm as air is being pumped into it. Find the ratio of surface areas of the balloon in the two cases.
Solution:
Surface area of sphere = 4πr2
Q5. A hemispherical bowl made of brass has inner diameter 10.5 cm. Find the cost of tin-plating it on the inside at the rate of 16 per 100 cm2.
Solution:
Curved surface area of hemisphere = 2πr2
Q6. Find the radius of a sphere whose surface area is 154 cm2.
Solution:
Area = 154 cm2
Surface area of sphere = 4πr2
Q7. The diameter of the moon is approximately one fourth of the diameter of the earth. Find the ratio of their surface areas.
Solution:
Let the diameter of earth = x
Q8. 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.
Solution:
Inner radius = 5 cm, width = 0.25 cm, radius = 5.25 cm
Curved surface area of hemisphere = 2πr2
⇒ 44 × 0.75 × 5.25
⇒ 173.25
Q9. A right circular cylinder just encloses a sphere of
radius r (see Fig. 13.22). Find
(i) surface area of the sphere,
(ii) curved surface area of the cylinder,
(iii) ratio of the areas obtained in (i) and (ii).
Solution:
Radius of sphere = r, radius of cylinder = r + r = 2r
(i) surface area of sphere = 4πr2
(ii) curved surface area of cylinder = 2πrh
⇒ 2πr(2r)
⇒ 4πr2
See other sub-topics of this chapter:
1. Exercise 13.1 2. Exercise 13.2 3. Exercise 13.3 4. Exercise 13.4 5. Exercise 13.5 6. Exercise 13.6 7. Exercise 13.7 8. Exercise 13.8 9. Exercise 13.9