A dealer sold an article at 6% loss. Had he sold it for Rs. 64 more, he would have made a profit of 10%. Then the cost of the article is = ?

Let the cost price of the article = Rs. 100x
Loss% = 6%
$$\eqalign{ & {\text{SP}} = 100x \times \frac{{94}}{{100}} = {\text{Rs}}{\text{.}}\,94x \cr & {\text{If}}\,{\text{SP}}\,{\text{is}}\,{\text{Rs}}{\text{.}}\,{\text{64}}\,{\text{more,}} \cr & \Rightarrow {\text{New}}\,{\text{SP}} = {\text{Rs}}{\text{.}}\,\left( {94x + 64} \right) \cr & \Rightarrow {\text{Profit}}\% \cr & \frac{{\left( {94x + 64} \right) - 100x}}{{100x}} \times 100 = 10 \cr & \Rightarrow 64 - 6x = 10x \cr & \Rightarrow 10x + 6x = 64 \cr & \Rightarrow 16x = 64 \cr & \Rightarrow x = \frac{{64}}{{16}} \cr & \therefore x = 4 \cr & \therefore {\text{Cost}}\,{\text{Price}} = 100 \times 4 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}{\text{.}}\,400 \cr} $$