Problema Solution
A health clinic uses a solution of bleach to sterilize petri dishes in which cultures are grown. The sterilization tank contains 80 gal of a solution of 4% ordinary household bleach mixed with pure distilled water. New research indicates that the concentration of bleach should be 7% for complete sterilization. How much of the solution should be drained and replaced with bleach to increase the bleach content to the recommended level?
Answer provided by our tutors
let 'x' represent the amount of solution that is drained and replaced with pure bleach
concentration = pure-bleach/total-volume
pure-bleach = concentration * total-volume
we have 80 gal of 4%, or 0.04*80
we want a concentration of 7%, or 0.07
we add 'x' gallons of pure bleach to 0.04*80 gallons of pure bleach:
0.07 = (x+0.04*(80-x))/(80)
solving for 'x' we have x=2.5
2.5 gallons of the current solution should be drained and replace with the same amount of pure bleach