Question

how many silver coins,1.75cm in diameter and of thickness 2mm, must be melted to form a cuboid of dimensions 5.5cm×10×3.5cm?​

Answer 1

Solution-

$\tt \:Radius = \frac{Diameter}{2} = \frac{1.75}{2} = 0.875 \: m \\ \\ \tt Volume \: of \: one \: coin = \pi {r}^{2} h \\ \\ \longrightarrow \: \tt \frac{22}{7} \times 0.2 \times 0.875 \times 0.875 = 0.48125 {cm}^{3} \\ \\ \tt Volume \: of \: cuboid = 5.5 \times 3.5 \times 10 = 192.5 {cm}^{3} \\ \\ \tt \: Number \: of \: coins = \frac{Volume \: of \: one \: coin}{Volume \: of \: cuboid } \\ \\ \longrightarrow \tt \: \frac{192.5}{0.48125} = 400 \: coins$