Problema Solution
A hospital needs 40L of a 15% solution of disinfectant. How many liters of a 20% solution and a 4% solution should be mixed to obtain this 15% solution?
Answer provided by our tutors
Let x and (40L-x) represent the 20% and 4% solutions respectively
Mixing the 20% and 1% to form 40L of 15% solution
.20x + .04(40L-x) = .15*40L
.16x = .11*40L
x = .11*40L/.16
x = 27.5L, the amount of the 20% solution.
12.5L,the amount of the 4% solution (40L - 27.5L)
.20*27.5L + .04*12.5L = 5.5L + .5L = 6L = .15*40L
Which tells us incidentally there is 6L of disinfectant in the final solution.