x sells two articles for Rs. 4000 each with no loss and no gain in the transaction. If one was sold at a gain of 25% the other is sold at a loss of = ?

Total SP = Rs. 8000 and Total CP = Rs. 8000
SP of 1^st articles = Rs. 4000
Gain on it = 25%
∴ CP of 1^st articles $$ = {\text{Rs}}{\text{.}}\,\left( {\frac{{100}}{{125}} \times 4000} \right) = {\text{Rs}}{\text{.}}\,3200$$
∴ CP of 2^nd articles = Rs. (8000 - 3200) = Rs. 4800
SP of 2^nd articles = Rs. 4000
∴ Loss on 2^nd articles
$$\eqalign{ & = \left( {\frac{{800}}{{4800}} \times 100} \right)\% \cr & = 16\frac{2}{3}\% \cr} $$