Helen mixes a first solution, 4 liters of 40% concentrated sulfuric acid solution, with a second solution, 5 liters of a sulfuric acid solution with a stronger concentration, and the resultant solution is 9 liters of 50% concentrated sulfuric acid solution. what was the concentration, as a percent, of the second solution?

58%

Explanation:

Formula used :

where,

and are the concentrations  of first and second solution respectively

is the concentration of resulting solution

and are the volumes of of first and second solution respectively

is the volume of resulting solution = 9 L

Now put all the given values in the above formula, we get the concentration of resulting solution.

solving for x, we get

The concentration of the second solution= 58%.