Marie has two solution of the same acid with different concentration
Solution A 12% - 20 liters
Solution B 36% - Unknown
And she wants to obtain a new solution C with at 20%
According to the proporcionality of the dissolution In mathematical terms will can write the following equation:
quantity of A * concentration A + quantity o B * concentration B = (qty A + qty B) * concentration C
20*0.12 + x*0.36 = (20+x) * 0.2
being x the unknown quantity of the solution B solving the equation:
2.4 + x*0.36 = 4 + x*0.2
x*0.36 - x*0.2 = 4 -2.4
x*0.16 = 1.6
x = 1.6/0.16 = 10
So the volume of solution B at 36% is 10 liters