Question

How many silver coins 1.75 cm of diameter and of thickness 2 mm must be melted to form a cuboid 11 cm x 10 cm x 7 cm?

• A. 1200
• B. 1400
• C. 1600
• D. 1000

Answer 1

The correct option is C 1600

Volume of cuboid $11\times 10\times 7=770c{m}^3$

$r=\frac{1.75}{2}=0.875cm$

$h=2mm=0.2cm$

Volume of the coin $\pi r^{2}h$

$=\frac{22}{7}\times 0.875\times 0.875\times 0.2$

$\therefore$ Required number of coins

=$\frac{volumeofthecuboid}{volumeofeachcoin}$

$=\frac{770\times 1000\times 1000\times 10\times 7}{22\times 875\times 875\times 2}$

$\frac{35\times 40\times 40\times 70}{35\times 35\times 2}$

$=40\times 40=1600$