Rs. 9800 are invested partly in 9% stock at 75 and 10% stock at 80 to have equal amount of incomes. The investment in 9% stock is:

Rs. 4800

Rs. 5000

Rs. 5400

Rs. 5600

Explanation:

Let the investment in 9% stock be Rs. $ x $.

Then, investment in 10% stock = Rs. $\left(9800 - x\right)$.

$ \dfrac{9}{75} \times x $ =$ \dfrac{10}{80} \times \left(9800 - x\right )$

$\Rightarrow \dfrac{3x}{25} $=$ \dfrac{9800 - x}{8} $

$\Rightarrow$ 24$ x $ = 9800 x 25 - 25$ x $

$\Rightarrow$ 49$ x $ = 9800 x 25

$\Rightarrow x $ = 5000.