Find the surface area of a sphere of diameter:
i) 14 cm  ii) 21 cm  iii) 3.5 m

Solution:

i) Diameter, d = 14 cm

Radius, r = 14cm/2 = 7cm

Surface area of a sphere = 4πr²

= 4 × 22/7 × 7cm × 7cm

= 616 cm²

ii) Diameter, d = 21 cm

Radius, r = 21cm/2

Surface area of a sphere = 4πr²

= 4/2 × 22/7 × 21/2 × 21/2

= 1386 cm²

iii) Diameter, d = 3.5 m

Radius, r = 3.5/2 = 1.75m

Surface area of a sphere = 4πr²

= 4 × 22/7 × 1.75m x 1.75m

= 38.5 m²

The surface area of a sphere with diameters 14 cm, 21 cm, and 3.5 m are 616 cm², 1386 cm², and 38.5 m² respectively.

☛ Check: NCERT Solutions for Class 9 Maths Chapter 13

Video Solution:

Find the surface area of a sphere of diameter: i) 14 cm ii) 21 cm iii) 3.5 m

Class 9 Maths NCERT Solutions Chapter 13 Exercise 13.4 Question 2

Summary:

It is given that there are spheres having diameters of 14 cm, 21 cm, and  3.5 m. We have found that the surface areas are 616 cm², 1386 cm², and 38.5 m² respectively.

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