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 blea

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Question 366383: 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?
Found 2 solutions by stanbon, josmiceli:
Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
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?
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Equation:
bleach - bleach + bleach = bleach
0.04*120 - 0.04x + 1.00x = 0.06*120
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Multiply thru by 100 to get:
4*120 - 4x + 100x = 6*120
96x = 2*120
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x = 2.5 gallons (amt. that should be drained and replaced by pure bleach)
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Cheers,
Stan H.

Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website!
Let = gallons of 4% solution to be drained
given:
Bleach in 4% solution:
gal
Bleach in removed portion:

Gallons of bleach added:

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In words:
(initial gallons of bleach - bleach removed + bleach added)/(total gallons) = 6%

2.5 gallons of 4% solution must be drained
and replaced with pure bleach