Question

How many coins of radius 1 cm and thickness 0.28 cm should be melted to form a soild cylinder of height 7 cm and diameter 8 cm.

Answer 1

Volume of one coin $=\frac{22}{7}\times r^2\times R$
r = 1cm
R = 0.28cm
$so,\frac{22}{7}\times 1\times 1\times 0.28$
Volume of social cylinder $=\frac{22}{7}\times 7\times 7\times 4$
$No.ofcoins=\frac{volumeofsoildcylinder}{volumeofonecoin}$
$=\frac{\frac{22}{7}\times 7\times \text{/}7\times \text{/}4\times 100}{\frac{22}{7}\times 1\times 1\times 0.\text{/}28}$
= 700