Question

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 6% 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 1

2.5 gal

Explanation:

let be x = galons of solution to be drained and replace with bleach

so, we have to substract to the current solution of bleach 0.04*120, x gallons that have a concentration of 0.04 x

and also, we have to add the same gallons of bleach to the solution, that is x

and have to obtain a final concentration of 0.06*120

we can express the problem with the follow equation:

0.04*120 - 0.04*x + x = 0.06*120

solving the equation for x:

4.8+0.96*x=7.2

0.96*x=7.2-4.8

0.96*x=2.4

x =2.5 gallons