Problema Solution
A health clinic uses a solution of bleach to sterilize petri dishes in which cultures are grown. The sterilization tank contains 120 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
concentration = pure-bleach/total-volume
pure-bleach = concentration * total-volume
let 'x' represent the amount of solution that is drained and replaced with pure bleach, then:
0.07 = (x + 0.04*(120-x))/(120)
solving for 'x' we have x=3.75
3.75 gallons should be drained and replaced with pure bleach