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Last updated at May 29, 2018 by Teachoo
Example 15 The height and the slant height of a cone are 21 cm and 28 cm respectively. Find the volume of the cone. Volume of the come = 1/3 ππ2β Given slant height = l = 28 cm Height of cone = h = 21 cm Let radius of cone = r cm We know that l2 = h2 + r2 282 = 212 + r2 282 β 212 = r2 r2 = 282 β 212 r2 = (28 β 21) (28 + 21) r2 = (7) (49) r = β("7(49)" ) r = β("7(7)2" ) r = 7β7cm So, Volume of the come = 1/3 ππ2β = 1/3 Γ 22/7 Γ 7 β7 Γ 7 β7 Γ 21 cm3 = 22 Γ 7β7 Γ 7 β7 cm3 = 22 Γ 7 Γ 7 Γ(β7)2 cm3 = 22 Γ 7 Γ 7 Γ 7 cm3 = 7546 cm3