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Question:

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

Solution:

(i) r = d/2 = 14/2 = 7cm, ⇒Surface Area = 4πr² = 4 × 22/7 × 7 × 7 = 616cm²
(ii) r = 21/2 = 10.5cm, ⇒Surface Area = 4 × 22/7 × 10.5 × 10.5 = 1386cm²
(iii) r = 3.5/2 = 1.75m ⇒Surface Area = 4πr² = 4 × 22/7 × 1.75/100 × 1.75/100 = 38.5m²