Surface Areas & Volumes | Exercise 13.4 | Q1

NCERT Solutions for Class 9 Math | Chapter 13 | Surface Area of Sphere

Question 1: Find the surface area of a sphere of radius:
(i) 10.5 cm
(ii) 5.6 cm
(iii) 14 cm


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Explanatory Answer | Exrecise 13.4 Question 1

Part (i): Radius of the sphere, r = 10.5 cm

Surface area of sphere = 4 × π × r2
Take π = \\frac{22}{7})
Surface area of sphere = 4 × \\frac{22}{7}) × 10.5 × 10.5
= 4 × 22 × 1.5 × 10.5
= 1386 cm2


Part (ii): Radius of the sphere, r = 5.6 cm

Surface area of sphere, r = 4 x π × r2
Take π = \\frac{22}{7})
Surface area of sphere = 4 × \\frac{22}{7}) × 5.6 × 5.6
= 4 × 22 × 0.8 × 5.6
= 394.24 cm2


Part (iii): Radius of the sphere, r = 14 cm

Surface area of sphere = 4 × π × r2
Take π = \\frac{22}{7})
Surface area of sphere = 4 × \\frac{22}{7}) × 14 × 14
= 4 × 22 × 2 × 14
= 2464 cm2

 


NCERT Solutions for Class 9 Math | Chapter 13 Video Solutions



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