The marked price of an article is increased by 25% and the selling price is increased by 16.66%, then the amount of profit doubles. If the original marked price be Rs. 400 which is greater than the corresponding cost price by 33.33% , what is the increased selling price?

Initially                 CP           profit            SP                MP

                              100           x               (100+x)         133.33

After Change     100           2x             (100+x)   

Now,   Since (100+x)  - 100 = 2x

            $\frac{7}{6}$ x= 20%

                         CP            Profit              SP             MP

                        100             20               120           133.33

So,                  300             60               360             400

Again             300            120              420

So the increased selling price = Rs. 420