The surface area of a sphere of radius 5 cm -Maths 9th

The surface area of a sphere of radius 5 cm -Maths 9th
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Answer :

Radius of the sphere (r1) = 5 cm Radius of the base of cone (r2) = 4 cm Let r сm be the height of the cone. Surface area of sphere = 4 πr2  ⇒ 4 π(5)2 = 100 π cm2  Curved surface area of cone = πrl = 4 πl cm2  where l is the slant height of the cone.  According to the statement,  100 π = 5(4 πl)    ⇒ l = 5 cm Now,  h2 = l2 - r2 = 52 – 42 = 32     ⇒ h = 3 cm  ∴ Volume of cone = 1/3 πr2h = 1/3 x 22/7 x 42 x 3 = 352/7 cm3 = 50.29 cm3   (Approximately)
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