A man sold two steel chairs for Rs. 500 each. On one, he gains 20% and on the other, he loses 12%. How much does he gain or lose in the whole transaction ?

Explanation:-

$$\eqalign{ & {\text{Total Selling Price}} \cr & = {\text{Rs}}.\left( {2 \times 500} \right) \cr & = {\text{Rs}}{\text{. }}1000. \cr & {\text{C}}{\text{.P}}{\text{. of first chair}} \cr & = {\text{Rs}}.\left( {\frac{{100}}{{120}} \times 500} \right) \cr & = {\text{Rs}}{\text{.}}\frac{{1250}}{3} \cr & {\text{C}}{\text{.P}}{\text{. of Second chair}} \cr & = {\text{Rs}}.\left( {\frac{{100}}{{88}} \times 500} \right) \cr & = {\text{Rs}}.\frac{{6250}}{{11}} \cr & {\text{Total C}}{\text{.P}}{\text{.}} \cr & = {\text{Rs}}.\left( {\frac{{1250}}{3} + \frac{{6250}}{{11}}} \right) \cr & = {\text{Rs}}.\left( {\frac{{32500}}{{33}}} \right). \cr & {\text{Gain}} = {\text{Rs}}.\left( {1000 - \frac{{32500}}{{33}}} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}.\left( {\frac{{500}}{{33}}} \right). \cr & \therefore {\text{Gain }}\% \cr & = \left( {\frac{{500}}{{33}} \times \frac{{33}}{{32500}} \times 100} \right)\% \cr & = 1.54\% \approx 1.5\% \cr}$$