Question

Find the number of coins $1.5$ cm in diameter and $0.2$ cm thick to be melted to form a right circular cylinder whose height is $8$ cm and diameter $6$ cm

Answer 1

Volume of the cylinder $=\pi r^{2}h$
$=\pi \times 3\times 3\times 8c{m}^3$
$=72\pi c{m}^3$
Volume of the coin $=\pi {\left(\frac{1.5}{2}\right)}^2\times \left(0.2\right)c{m}^3$
$=\frac{9}{80}\pi c{m}^3$
$\therefore$ Number of coins $=\frac{Vol.ofcylinder}{Vol.ofacoin}$
$=72\pi ÷\frac{9\pi }{80}$
$=640$