In a shop, 80% of the articles are sold at a profit of 10% and the remaining at a loss of 40%. What is the overall profit/loss ?

Answer: Option D

Let the total C.P. of all the articles be Rs. x.
Then,
C.P. of 80% of the articles = 80% of Rs. x.
$$=\text{Rs}.\frac{4x}{5}$$
C.P. of the remaining articles
$$\begin{array}{rl}& =\text{Rs}.\left(x-\frac{4x}{5}\right)\\ & =\text{Rs}.\frac{x}{5}\\ & \text{Total S}\text{.P}\text{.}\\ & =Rs.\left(110\%\text{ of }\frac{4x}{5}+60\%\text{ of }\frac{x}{5}\right)\\ & =\text{Rs}.\left(\frac{22x}{25}+\frac{3x}{25}\right)\\ & =\text{Rs}\text{. }x.\end{array}$$
Since C.P. = S.P. there is no profit no loss