CBSE Notes, Lectures

CBSE - Mathematics - Surface Areas and Volumes

Surface Areas and Volumes

NCERT Exercise Exercise 13.4

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

(i) Radius of the sphere (r) = 10.5 cm
Surface area = 4πr2
                    = (4 × 22/7 × 10.5 × 10.5) cm2
                    = 1386 cm2

(ii) Radius of the sphere (r) = 5.6 cm
Surface area = 4πr2
                     = (4 × 22/7 × 5.6 × 5.6) cm2
                     = 394.24 cm2

(iii) Radius of the sphere (r) = 14 cm
Surface area = 4πr2
                     = (4 × 22/7 × 14 × 14) cm2
                     = 2464 cm2

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