Alligation or Mixture - General Questions

A mixture of 30 litres contains milk and water in the ratio 4 : 2. If 4 litres of water is added, what is the new ratio of milk to water?

In what ratio must rice at Rs. 44 per kg be mixed with rice at Rs. 65 per kg so that the mixture costs Rs. 52 per kg?

In what ratio must rice at Rs. 36 per kg be mixed with rice at Rs. 69 per kg so that the mixture costs Rs. 67 per kg?

In what ratio must rice at Rs. 24 per kg be mixed with rice at Rs. 48 per kg so that the mixture costs Rs. 29 per kg?

In what ratio must rice at Rs. 31 per kg be mixed with rice at Rs. 58 per kg so that the mixture costs Rs. 54 per kg?