Question

Howany silver coins, 1.75 cm in diameter and of thickness 2mm, must be melted to form a cuboid of dimensions 5.5cm x 10cm x 3.5 cm?
(only calculation part)

Answer 1

Let number of silver coins be n

Volume of cuboid = length × breadth × height = 5.5 × 10 × 3.5 = 192.5 cm3

Silver coin is a cylinder. Thickness of silver coin is height of cylinder.
Height of coin (cylinder) = h = 2 mm = 0.2 cm

Diameter of coin (cylinder) = d = 1.75 cm

Radius of silver coin (cylinder) = r=d2=1.752=0.875cm
Volume of silver coin (cylinder) = πr2h=227×0.875×0.875×0.2=0.48125cm3
According to given condition we have

n × Volume of coin = Volume of cuboid

⇒ n × 0.48125 = 192.5

⇒192.50.48125=400