Question 339805
a sterilization tank contains 120 gallons of a solution of 6% bleach mixed with pure distilled water. for complete sterilization, the solution only needs to be at 4%. how much of the solution needs to be drained and replaced with water to reduce the concentration of bleach. 
note:: u want to still have 120 gallons of solution when you are finished diluting.
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Equation:
bleach - bleach + bleach = bleach
0.06*120 - 0.06x + 0x = 0.04*120
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Multiply thru by 100 to get:
6*120 - 6x + 0 = 4*120
6x = 2*120
x = 40 gallons (amt. of 6% solution that must be replaced by water)
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Cheers,
Stan H.