A trader mixes 26 kg of rice at Rs. 20 per kg with 30 kg of rice of other variety at Rs. 36 per kg and sells the mixture at Rs. 30 per kg. His profit percent is:

$$\eqalign{ & {\text{C}}{\text{.P}}{\text{. of 56 kg rice}} \cr & = {\text{ }}Rs.{\text{ }}\left( {26{\text{ }} \times {\text{ }}20{\text{ }} + {\text{ }}30{\text{ }} \times {\text{ }}36} \right) \cr & = {\text{ }}Rs.{\text{ }}\left( {520{\text{ }} + {\text{ }}1080} \right) \cr & = {\text{ }}Rs.{\text{ }}1600 \cr & {\text{S}}{\text{.P}}{\text{. of 56 kg rice}} \cr & = {\text{ }}Rs.{\text{ }}\left( {56{\text{ }} \times {\text{ }}30} \right) \cr & = {\text{ }}Rs.{\text{ }}1680 \cr & \therefore {\text{Gain}} = \left( {\frac{{80}}{{1600}} \times 100} \right)\% \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 5\% \cr} $$