Question

How many gold coins of 1.75cm in diameter and 2mm in thickness can be melted to form a cuboid of dimensions 5.5cm x 10cm x 3.5cm?

• A. 550
• B. 350
• C. 500
• D. 400

Answer 1

The correct option is D

400

Radius of the coin = 0.875cm

Height of coin = 0.2 cm

Volume of the cylinder = $\pi r^2{h}^{\prime }=\frac{22}{7}\times (0.875{)}^2\times 0.2=0.481c{m}^3$

Volume of cuboid = l × b × h = 5.5 × 10 × 3.5 = 192.5 \(cm^3\)

Let x be the number of coins that can be made

So, $x=\frac{Volumeofthecuboid}{Volumeofthecylinder\left(coin\right)}=\frac{192.5}{0.481}=400coins$