Question

How many silver coins, 1.75 cm in diameter and thickness 2 mm., need to be melted to form a cuboid of dimensions 5.5 cm × 10 cm × 3.5 cm?

Answer 1

Let the number of silver coins needed to melt = n 

Then total volume of n coins = volume of the cuboid 

n × πr²h = lbh [∵ The shape of the coin is a cylinder and V = πr²h]

∴ 400 silver coins are needed.