SOLUTION: Jill decides to move her fish from a 20 gallon aquarium to a 50 gallon aquarium. She added 3 tablespoons of salt to her old aquarium. If she wishes to maintain to same salinity l

Question 969351: Jill decides to move her fish from a 20 gallon aquarium to a 50 gallon aquarium. She added 3 tablespoons of salt to her old aquarium. If she wishes to maintain to same salinity level, how many tablespoons should she add to her new aquarium? Please show how you got the answer.
Found 2 solutions by josmiceli, Boreal:
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Set Up a ratio:
[ gallons ] / [ gallons ] = [ tbspns ] / [ tbspns ]

She should add 7.5 tablespoons to her new aquarium
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
This is a proportion problem and is solved by cross multiplication.
3 tablespoons of salt is to 20 gallons as x tablespoons is to 50 gallons.
You know you will need more salt. Because 50 gallons is more than double 20 gallons, you will need more than double 3 tablespoons, so the answer has to be more than 6.
(3/20)=(x/50)
Cross-multiply: 3*50=x *20
20 x = 150
x=7.5 tablespoons The answer makes sense.
You can also do this by recognizing that 50 is 2 and a half times 20. Therefore, the tablespoons need to be 2 and a half times 3, or 7.5.
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