A hollow cylindrical tube 20 cm long is made of iron and its external and internal diameters are 8 cm and 6 cm respectively. The volume (in cubic cm) of iron used in making the tube is (Take pi; = 22/7)
volume of hollow cylinder = pi;(r12 minus; r22)h h = 20 r1 (external radius) = external diameter divide;2 = 8divide;2 = 4 r2 (internal radius) = internal diameter divide;2 = 6divide;2 = 3 volume of hollow cylinder = pi;(42- 32) 20 = 22/7 (7)20 = 440
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