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]

Answer 1

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.