SOLUTION: john needs to mix 10% saline solution with 30% saline to create 200 milliliters of 18% solution. How much milliliters must john use?

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Question 714005: john needs to mix 10% saline solution with 30% saline to create 200 milliliters of 18% solution. How much milliliters must john use?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
x and y for volume to use of the 10% saline and for the 30% saline.
%2810x%2B30y%29%2F200=18 AND x%2By=200.

%281x%2B3y%29%2F20=18
x%2B3y=20%2A18
x%2B3y=360

Solve this system for x and y:
highlight%28x%2B3y=360%29
highlight%28x%2By=200%29

The easiest way to continue is subtract the second equation from the first equation (of the system, of course) to very easily obtain a value for y, the volume to use of the 30% saline.