The density of a material in CGS system is $8 g / cm^3$. In a system of a unit in which unit of length is 5 cm and unit of mass is 20 g. The density of material is :

8 20 50 80

50

The correct answer is Option (3) → 50 $n_1u_1=n_2u_2$ $∴n_2=n_1\frac{u_1}{u_2}=8\left[\frac{M_1}{M_2}\right]\left[\frac{L_2}{L_1}\right]^3$ $=8\left[\frac{1}{20}\right]\left[\frac{5}{1}\right]^3=50$