The reduction of 20% in the price of rice enables a person to obtain 50 kg more for Rs. 450. Find the original price of rice per kg.

$$\eqalign{ & {\text{Reduction of money}} = 450 \times \frac{{20}}{{100}} = 90 \cr & {\text{After reduction price}} = \frac{{90}}{{50}} = {\text{Rs}}{\text{. }}1.8{\text{ per kg}} \cr & {\text{Increase in price }}20\% = \frac{1}{5} \cr & {\text{4 unit}} = \frac{9}{5} \cr & {\text{1 unit}} = \frac{9}{{5 \times 4}} \cr & {\text{5 unit}} = \frac{9}{{5 \times 4}} \times 5 = \frac{9}{4} = {\text{Rs}}{\text{. }}2.25 \cr} $$