A and B started a business investing amounts in the ratio of 2 : 3. If A has invested an additional amount of Rs. 10000, their ratio of investment would have been 3 : 2. The amount invested by A was ?

Answer: Option A

Initial ratio of investments by A and B = 2 : 3
Let their respective investments are 2x and 3x
According to the question,
If A added Rs. 10000 to his investment
Then the new ratio = 3 : 2
$$\begin{array}{rl}& \Rightarrow \frac{2x+10000}{3x}=\frac{3}{2}\\ & \Rightarrow 4x+20000=9x\\ & \Rightarrow 5x=20000\\ & \Rightarrow x=4000\end{array}$$
Original investment by A = 2 × 4000 = Rs. 8000