SOLUTION: A chemist needs 120millileters of a 21% solution but has only 11% and 71% solutions avaible. Find how many millileters of each that should be mixed to get the desired solution.

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Question 715922: A chemist needs 120millileters of a 21% solution but has only 11% and 71% solutions avaible. Find how many millileters of each that should be mixed to get the desired solution.
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
(target matter)/(amount of solution)=(target concentration)

x = volume of 11%
y = volume of 71%

%2811x%2B71y%29%2F120=21 and x%2By=120

Rational equation gives us
11x+71y=120*21
11x%2B71y=2520

Solve the system for x and y:
11x%2B71y=2520
x%2By=120

Multiplying the simple "120" equation by 11, then we have 11x%2B71y=2520 and 11x%2B11y=1320. Subtract the second equation from the first and ... find a value for y. Then use the simpler x+y=120 equation to find the value for x.

11x%2B71y-11x-11y=2520-1320
60y=1200, 6y=120
highlight%28y=20%29, ml. of the 71% solution...