Question

How many silver coins, $1.75cm$ in diameter and of thickness $2mm$, must be melted to form a cuboid of dimensions $5.5cm\times 10cm\times 3.5cm$?

Answer 1

Let the number of coin be $x$

$x\times$ volume of 1 coin $=$ volume of box

$x\times \pi r^{2}h=l\times b\times h$

$x\times \frac{22}{7}\times \frac{175}{100\times 2}\times \frac{175}{100\times 2}\times \frac{2}{10}=\frac{55}{10}\times 10\times \frac{35}{10}$

$x=\frac{55\times 35\times 100\times 100\times 2}{22\times 25\times 175}$

$=20\times 20$

$=400coins$