SOLUTION: a 70% acid solution is to be mixed with water to produce a 5 liter mixture containing 28% acid. How many milliliters of water and how many milliliters of the 70% acid solution are

Let x = the amount of water (in liters), and y = the amount of the 70% acide solution.



First equation is for the total volume of the solution

x + y = 5     liters.     (1)



Second equation is for the final mixture concentration

 = 0.28     (2)  (concentration is the ratio of the pure acid volume to the total liquid volume)



From equation (2)  you get   y =  = 2.


Then from equation (1) the rest,  5-2 = 3 liters is the water volume.



Answer.  2 liters of water and 3 liters of the 70% solution to be mixed.


Check.    = 0.28 = 28%.    ! Correct !