Consider three jars, labelled Jar 1, Jar 2 and Jar 3.
Jar 1 contains four liters of a solution that is 45% acid.
Jar 2 contains five liters of a solution that is 48% acid.
Jar 3 contains one liter of a solution that is n% acid.
From jar 3, x/y liters of the solution is added to jar 1, and the remainder of the solution in jar 3 is added to jar 2, where x and y are relatively prime positive integers.
At the end, each jar 1 and jar 2 contain solutions that are 50% acid.