How many coins 1.75 cm in diameter and 2 mm thick must be melted to form a cuboid 11 cm×10 cm×7 cm ?
A coin is a cylinder of diameter 1.75 cm and thickness (height of cylindrical shaped coin) is
radius of coin=1.752cm
and height of coin=210=0.2cm
∴ Volume of 1 coin = Volume of cylinder =πr2h=π×(1.752)2×0.2 cm3
Dimension of cuboid are 11 cm, 10 cm and 7 cm
∴ Volume of cuboid =l×b×h=70×11×7=770 cm3
According to question given,
Volume of cuboid = Number of coins × Volume of each coin
=>770=No of coins×π×(1.752)2×0.2 cm3
=>No of coins=770227×(1.752)2×0.2
Hence, 1600 coins are required to form a cuboid of given dimensions.