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A solid iron sphere of diameter 6 cm is melted and made into a hollow cylindrical pipe of external diameter 10 cm and of length 4 cm. The thickness of the pipe is:1). 1 cm2). 2 cm3). 4 cm4). 8 cm |
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Answer» The volumes of the SPHERE and of the PIPE will be the same. Diameter of sphere = 6 cm ∴ RADIUS of sphere = 6/2 = 3 cm Volume of the sphere = 4πr3/3 = 4π(3)3/3 = 36π Let the internal radius of pipe be r. Volume of the hollow cylindrical pipe = πh (R2 – r2) where h= HEIGHT, R = external radius= 10/2 = 5 cm. Hence, 36 π = π (4)(52 – r2) ⇒ 25 – r2 = 9 ⇒r2 = 16 ⇒ r = 4 cm ⇒ Thickness = R – r = 5 – 4 = 1 cm |
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