Alloy A is formed by mixing iron (Fe) and nickel (Ni) in the ratio 3 : 4, while alloy B is formed by mixing Fe and Ni in the ratio 9 : 5. If equal quantities of alloys A and B are melted together to form a new alloy C, what will be the ratio of Fe to Ni in alloy C?

A vessel has 20 litres of milk. From this vessel, 5 litres of milk is taken out and replaced by water. The process is repeated once more. Find the quantity of milk (in litres) remaining in the vessel.

A shopkeeper mixes 40 kg of rice costing ₹30/kg with 60 kg of rice costing ₹50/kg. What is the average price (in ₹/kg) of the mixture?