Explanation:

Where we want to keep the expenditure same, There the Price ratio and Quantity ratio is in reverse order.

Price Ratio:-

10 : 9

Quantity Ratio:-

9 : 10

Increased Value of Quantity => 1 unit ---------> 6.2 kgs

                                           => 10 units --------> 10 * 6.2 = 62 kgs.

Now 62 kgs is bought in Rs.1116.

So New(Reduced) price per kg is => 1116/62 = 18 Rs./kg