Find the ratio at which rice at Rs.15.20 per kg is mixed with rice at Rs.18.10 per kg to get a mixture worth Rs.16.30 per kg.

​Price of first type of rice = Rs. 15.20/kg

Price of second type of rice = Rs. 18.10/kg

Price of the mixture = Rs. 16.30/kg

​Let's assume we mix x kg of rice at Rs. 15.20/kg with y kg of rice at Rs. 18.10/kg.

Cost of x kg of rice = 15.20x

Cost of y kg of rice = 18.10y

Total cost = 15.20x + 18.10y

Total weight = x + y

​$$\text{Price per kg} = \frac{\text{Total Cost}}{\text{Total Weight}}$$

​​

​$$16.30 = \frac{15.20x + 18.10y}{x + y}$$

​​$$16.30x + 16.30y = 15.20x + 18.10y$$​​

​$$1.10x = 1.80y$$​​

​$$\frac{x}{y} = \frac{1.80}{1.10} \\\frac{x}{y} = \frac{18}{11}$$

​​Therefore, the ratio of the two types of rice is 18:11.