Question

pls help me to solve this q

Answer 1

There are initially 2 litres. At the one hour mark we remove a litre to get 1 litre. At 1.5 hours we add half a liter to get 1.5 liters. At 2 hour mark we remove a litre to get 0.5 litres. At 2.5 hour mark we add half a litre to get 1 litre. At 3 hour mark we remove a litre to get 0 litres, and we are finished. Thus, the answer is 3 hours.