Q10 of 31 Page 1

Find the number of coins of 1.5 cm diameter and 0.2 cm thickness to be melted to form a right circular cylinder of height 10 cm and diameter 4.5 cm.

Given


Diameter of coin, d1 = 1.5 cm


Radius of coin, r1 = 0.75 cm [∵ diameter = 2 × radius]


Height of coin, h1 = 0.2 cm


Diameter of cylinder, d2 = 4.5 cm


Radius of cylinder, r2 = 2.25 cm


Height of cylinder, h2 = 10 cm


Formula


Volume of cylinder = πr2h


Where,


r = base radius of cylinder


h = height of cylinder


As, the cylinder is melted to form coins,


⇒ Number of coins formed



=


= 450 coins


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