The sum of the salaries of A and B is Rs. 2100. A spends 80% of his salary and B spends 70% of his salary. If their savings are in the proportion of 4 : 3, then what is the salary of A?

Answer: Option D

Clearly, A and B save 20% and 30% of their respective salaries
Let the salaries of A and B be x and y respectively
Then,
$$\begin{array}{rl}& \text{ = }\frac{\text{20}\%\text{ of }x}{\text{30}\%\text{ of }y}=\frac{4}{3}\\ & \Rightarrow \frac{x}{5}\times \frac{10}{3y}=\frac{4}{3}\\ & \Rightarrow \frac{x}{y}=2\\ & \Rightarrow x=2y\\ & \therefore x+y=2100\\ & \Rightarrow 2y+y=2100\\ & \Rightarrow 3y=2100\\ & \Rightarrow y=700\\ & \text{A’s salary}=x=2y\\ & =\text{Rs}\text{. }\left(2\times 700\right)\\ & =\text{Rs}\text{. }1400\end{array}$$