How many liters of a 10% acid solution must be mixed with 10 L of a 4% solution to obtain a 6% solution?
Let x litres of 10% acid solution be mixed
Acidic content in the final solution after mixing = sum of the acidic content in the two mixing solutions
6*(10+x)/100 = [10x/100] + [410/100]
or, x = 5
Thus, 5 litres of 10% acidic solution is require