SOLUTION: A chemist needs 120 milliliters of a 34% solution but has only 7% and 43% solutions available. Find how many milliliters of each that should be mixed to get the desired solution.

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Question 1188015: A chemist needs 120 milliliters of a 34% solution but has only 7% and 43% solutions available. Find how many milliliters of each that should be mixed to get the desired solution.
Found 2 solutions by josgarithmetic, greenestamps:
Answer by josgarithmetic(39617) (Show Source):
You can put this solution on YOUR website!
v, volume of the 43%
120-v, volume of the 7%

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Answer by greenestamps(13200) (Show Source):
You can put this solution on YOUR website!

Here is a quick and easy method for solving any "mixture" problem like this if the numbers are "nice" (and if a formal algebraic solution is not required).

(1) On a number line, the 34% is 3/4 of the way from 7% to 43%. (7 to 43 is a difference of 36; 7 to 34 is a difference of 27; 27/36 = 3/4.)
(2) That means 3/4 of the mixture needs to be the 43% ingredient.

ANSWER: 3/4 of 120ml, or 90ml, of 43%; the other 30ml of 7%

CHECK:
0.34(120) = 40.8
0.43(90)+0.07(30) = 38.7+2.1 = 40.8