SOLUTION: How many liters of pure baking soda must be added to 180 liters of a 40% baking soda solution to get a 70% baking soda solution?

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Question 432501: How many liters of pure baking soda must be added to 180 liters of a 40% baking soda solution to get a 70% baking soda solution?
Found 2 solutions by josmiceli, htmentor:
Answer by josmiceli(9697) (Show Source):
You can put this solution on YOUR website!
In words:
(liters of pure baking soda in final solution)/(liters of final solution) = 70%
Let = liters of pure baking soda to be added
given:
Pure baking soda in 40% solution is
-----------------

180 liters of pure baking soda must be added
check:

OK

Answer by htmentor(789) (Show Source):
You can put this solution on YOUR website!
The initial amount of baking soda in the 40% solution = 0.40*180 = 72 liters
Let x = the number of liters of baking soda to add
For a 70% solution we have
0.70 = (72+x)/(180+x)
since the same amount, x, is added to the solution and the original amount of baking soda
Solve for x:
0.7(180+x) = 72+x
126 + 0.7x = 72 + x -> 0.3x = 72 -> x = 180 liters
Check:
(72+180)/(180+180) = 252/360 = 0.7