Question

The density of a material in SI units is $128 \; kg \; m^{-3}$. In certain units in which the unit of length is $25\, cm$ and the unit of mass is $50\, g$, the numerical value of density of the material is :

• A. 410
• B. 640
• C. 16
• D. 40

Answer 1

Answer: (D)

40

Answer 2

$\frac{128 kg}{m^{3}} = \frac{125 \left(50g\right)\left(20\right)}{\left(25cm\right)^{3}\left(4\right)^{3}}$
$= \frac{128}{64} \left(20\right)units$
$= 40\, units$