Shailja earns 15 percent on an investment but loses 10 percent on another investment. If the ratio of the two investments is 3 : 5, then the combined loss percent is -

Answer: Option A

Let the two investments be Rs. 3x and Rs. 5x respectively.
Then,
Total investment = Rs. (3x + 5x) = Rs. 8x
Total output = Rs. (115% of 3x + 90% of 5x)
= Rs. (3.45x + 4.5x) = Rs. 7.95x
Loss = Rs. (8x - 7.95x) = Rs. 0.05x
$$\begin{array}{rl}& \therefore \text{Loss percent}\\ & =\left(\frac{0.05x}{8x}\times 100\right)\%\\ & =\frac{5}{8}\%\end{array}$$