A solid metal cylinder of 10 cm height and 14 cm diameter is melted and re - cast into two cones in the propor

Question

A solid metal cylinder of 10 cm height and 14 cm diameter is melted and re - cast into two cones in the proportion of 3 : 4 (volume), keeping the height 10 cm. What would be the percentage change in the flat surface area before and after?

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Accepted Answer

50%. Volume of Cylinder = π r 2 h = π × 7 2 × 10 = 490 π \pi r^2 h = \pi 	imes 7^2 	imes 10 = 490\pi π r 2 h = π × 7 2 × 10 = 490 π Now, The solid metal cylinder is re-cast into two cones in the proportion 3 : 4 i.e. the volumes of cone 1 and cone 2 is 210 π 210 \pi 210 π and 280 π 280 \pi 280 π respec