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Question
How many silver coins, 1.75 cm in diameter and of thickness 2 mm, must be melted to form a cuboid of dimensions 5.5 cm × 10 cm × 3.5 cm? [Use π=22/7]
Solution
Coins are cylindrical in shape.
Height (h1) of cylindrical coins = 2 mm = 0.2 cm
Radius (r) of circular end of coins = 1.75/2 =0.875 cm
Let n coins be melted to form the required cuboids.
Volume of n coins = Volume of cuboids
nxπxr2xh1 = lxbxh
n x π x (0.875)2 x 0.2 = 5.5 x 10 x 3.5
`n = (5.5xx10xx3.5xx7)/((0.875)^2xx0.2xx22) = 400`
Therefore, the number of coins melted to form such a cuboid is 400.
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