Pure acid is to be added 5% acid solution to obtain 95 liter of 69% solution. What amounts of each should be used? How many liters of the 5% solution should be in the mixture,

Ratio of

pure acid : 5%

= (69-5) : (100-69)

= 64 : 31

Out of 95L of mixture,

Pure acid=95 (64 / (64+31)) = 95 * (64/95) = 64 L

5% acid = 95 (31 / (64+31)) = 95 * (31/95) = 31 L

Check: total=64+31=95L ok.