5.74 g of a substance occupies $1.2c{m}^3.$  Keeping the significant figure in view, its density is given by

There are 3 significant figures in the measured mass whereas there are only 2 significant figures in the measured volume. Hence, the density should be expressed to only 2
significant figures. 

$\because Density=\frac{Mass}{Volume}$

$\therefore Density=\frac{5.74}{1.2}gc{m}^{-3}=4.8gc{m}^{-3}$