If 40% of a number is less than its 60% by 30, then the 20% of that number is:

Answer: Option D

$$\begin{array}{rl}& \text{Let the number be }x\\ & \frac{x\times 40}{100}=\frac{x\times 60}{100}-30\\ & 40x=60x-3000\\ & 20x=3000\\ & x=150\\ & \frac{x\times 20}{100}=\frac{150\times 20}{100}=30\end{array}$$