In a town 25% of the persons earned more than Rs. 45000 where as 75% earned more than Rs. 18000. The relative dispersion will be?

Dear student, 
As per the question it is given that
Third quartile (Q₃) = 45000
First quartile ​(Q₁) = 18000

Relative value of dispersion is coefficient of quartile deviation
$$\begin{gathered} Coefficient of quartile deviation = \frac{Q_3-Q_1 }{Q_3+Q_1} \\ Coefficient of quartile deviation = \frac{45000 - 18000 }{45000 + 18000} = 0.428 \end{gathered}$$