The monthly incomes of two families A and B are shown by the following diagrams: If the income of the family B is Rs. 12000, then the income of family A would be:

Answer: Option D

Ratio of the monthly incomes of families A and B
= Ratio of the areas of rectangles A and B
= 5 × 2 : 4 × 1
= 10 : 4
= 5 : 2
Let the monthly income of family A be Rs. x
Then,
5 : 2 :: x : 12000
⇒ 2x = 5 × 12000 = 60000
$$\begin{array}{rl}& \Rightarrow x\text{ = }\frac{60000}{2}\\ & =30000\end{array}$$