SOLUTION: Please help. Thankyou. An aquarium owner tested the chemical levels of the water in her 50 gallon tank. The water tested with a level of 2% of a certain chemical. She wanted to

Algebra ->  Customizable Word Problem Solvers  -> Mixtures -> SOLUTION: Please help. Thankyou. An aquarium owner tested the chemical levels of the water in her 50 gallon tank. The water tested with a level of 2% of a certain chemical. She wanted to      Log On

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Question 719910: Please help. Thankyou.
An aquarium owner tested the chemical levels of the water in her 50 gallon tank. The water tested with a level of 2% of a certain chemical. She wanted to drop the level to a safe level of 1.25% How much of the aquarium water should be removed and pure water added to the aquarium?

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = gallons of water to be removed and
replaced with pure water
The owner starts out with +.02%2A50+=+1+ gallon of the chemical
The gallons of chemical that are removed when the water is drained
is +.02x+
Note that there are 50 gallons at the start and 50 gallons at the end
----------------
+%28+1+-+.02x+%29+%2F+50+=+.0125+
+1+-+.02x+=+.0125%2A50+
+1+-+.02x+=+.625+
+.02x+=+1+-+.625+
+.02x+=+.375+
+x+=+18.75+
18.75 gallons should be drained and replaced with pure water
check:
+%28+1+-+.02%2A18.75+%29+%2F+50+=+.0125+
+%28+1+-+.375+%29+%2F+50+=+.0125+
+.625+%2F+50+=+.0125+
+.625+=+.625+
OK