In what ratio should wheat at ₹38 per kg be mixed with wheat at ₹26 per kg so that on selling the mixture at ₹39 per kg, there would be a profit of 30%?

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?