A jar contains a mixture of 2 liquids A and B in the ratio 4 : 1. When 10 litres of the mixture is taken out and 10 litres of liquid B is poured into the jar, the ratio becomes 2 : 3. How many litres of liquid A was contained in the jar initially?

Let initially, there be 4V litres of A and V litres of B in the solution. Now, when 10 litres of solution is taken out, we have (4V - (4/5) x 10) lkitres or 4V - 8 litres of A left in solution. In the 10 litres of solution taken out, 2 litres of B will go out. Thus, B left in solution = (V - 2) litres. After 10 litres of B is added, B in the solution = (V - 2 + 10) litres = (V + 8) litres. Now, (quantity of liquid A in solution) / (quantity of liquid B in solution) = (4 V - 8) / (V + 8) = 2 /3. On solving, we get V = 4. Thus, initial quantity of A in the solution = 4 V = 4 x 4 litres = 16 litres.