Word Problem

Question

How much water should be added to 1 gallon of pure antifreeze to obtain a solution that is 95% antifreeze?

Answer 1

Here is another way to set up the solution.  (It will give the same answer as Michael's solution.)

 

w = number of gallons of pure water

You have 1 gallon of pure antifreeze

You want 95% antifreeze in 1+w gallons

 

You can do a weighted combination of concentrations of antifreeze.

 

(0%)(w) + (100%)(1) = (95%)(1 + w)

 

100 = 95(1 + w)

 

w = 100/95 - 1 ≅ 0.0526 gallons

Answer 2

Let the amount of added water be W gallons.

After it is added we have 1/(1+W)=.95

You may take it from here.