Question

Find the number of coins of 1.5 cm diameter and 0.2 cm thickness to be melted to form a right circular cylinder of height 5 cm and diameter 4.5 cm.

Answer 1

Here,
Height. =0.2cm. (Of Coin)
Diameter =1.5cm. (Of Coin)
Radius. =1.5/2cm(Of coin)

Now,Of Cylinder
Height. =5cm
Diameter=4.5cm
Radius. =4.5cm/2

No. of coins required=
$\frac{vol. \: of \: cylinder}{vol. \: of \: coin}$
$\frac{\pi \gamma {}^{2}h }{\pi \gamma {}^{2} h}$
$\frac{(4.5 \div 2) {}^{2} \times 5}{(1.5 \div 2) {}^{2} \times 0.2 }$
$\frac{21.3125}{0.1125}$
189.44