Two articles are bought at the same price. One is sold at 20% profit and the other is sold at 10% loss. The overall profit/loss percentage is:

Two articles are bought at the same price.

Let's assume the cost price of each article is 100y.

So the total cost price of both article = (100y+100y) = 200y    Eq.(i)

One is sold at 20% profit.

The selling price of one article = 100y of (100+20)%

= 100y of 120%

= 120y

Other is sold at 10% loss.

The selling price of other article = 100y of (100-10)%

= 100y of 90%

= 90y

So the total selling price of both article = 120y+90y = 210y    Eq.(ii)

Overall profit percentage = $$\frac{\left(Eq.(ii)-Eq.(i)\right)}{Eq.(i)}\times100$$

= $$\frac{\left(210y-200y\right)}{200y}\times100$$

= $$\frac{10y}{200y}\times100$$

= 5%