Rs. 12 प्रति लीटर की लागत वाले एक तरल में पानी (लागत Rs. 0) को किस अनुपात में मिलाया जाना चाहिए ताकि मिश्रित तरल को Rs. 13.75 प्रति लीटर पर बेचने पर 25% का लाभ प्राप्त हो?

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?