A metallic block 12.0 cm long, 2 cm thick and 3.5 cm wide has a mass of 1800 g. Calculate the density of the metal.

Length= 12.0 cm, Breadth= 3.5 cm, 

Thickness = 2 cm

Volume = Length x Breadth x Thickness

$\begin{array}{l}\mathrm{Volume}=12\mathrm{cm}\times 3.5\mathrm{cm}\times 2\mathrm{cm}=84.0{\mathrm{cm}}^3\\ \text{ Density }=\frac{\text{ Mass }}{\text{ Volume }}=\frac{1800 \mathrm{g}}{84.0{\mathrm{cm}}^3}\\ \mathrm{Density}=21.43{\mathrm{gcm}}^{-3}\end{array}$