Find the surface area of a sphere of radius: (i) 10.5cm (ii) 5.6cm (iii) 14cm -Maths 9th

Find the surface area of a sphere of radius: (i) 10.5cm (ii) 5.6cm (iii) 14cm -Maths 9th
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Formula: Surface area of sphere (SA) = 4πr2 (i) Radius of sphere, r = 10.5 cm SA = 4×(22/7)×10.52 = 1386 Surface area of sphere is 1386 cm2 (ii) Radius of sphere, r = 5.6cm Using formula, SA = 4×(22/ 7)×5.62 = 394.24 Surface area of sphere is 394.24 cm2 (iii) Radius of sphere, r = 14cm SA = 4πr2 = 4×(22/7)×(14)2 = 2464 Surface area of sphere is 2464 cm2 Find the surface area of a sphere of diameter: (i) 14cm (ii) 21cm (iii) 3.5cm (Assume π = 22/7) Solution: (i) Radius of sphere, r = diameter/2 = 14/2 cm = 7 cm Formula for Surface area of sphere = 4πr2 = 4×(22/7)×72 = 616 Surface area of a sphere is 616 cm2 (ii) Radius (r) of sphere = 21/2 = 10.5 cm Surface area of sphere = 4πr2 = 4×(22/7)×10.52 = 1386 Surface area of a sphere is 1386 cm2 Therefore, the surface area of a sphere having diameter 21cm is 1386 cm2 (iii) Radius(r) of sphere = 3.5/2 = 1.75 cm Surface area of sphere = 4πr2 = 4×(22/7)×1.752 = 38.5 Surface area of a sphere is 38.5 cm2
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