Questions on Word Problems: Mixtures answered by real tutors!

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Let's call the amount from beaker A, A.
Let's call the amount from beaker B, B.
The total final volume is 6 liters.
1.
The final concentration is 18%.
2.
Let's multiply equation 2 by 100 to get rid of decimals.
2.
2.
2.
We can use eq. 2 to solve for B in terms of A.
2.


Now substitute this into eq. 1 and solve for A.
1.



Now back substitute to find B,



2.4 liters of solution A and 3.6 liters of solution B.

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In words:
(liters of acid in beaker A) + (liters of acid in beaker B) / (total liters of solution in A and B) = % solution of acid
Let A = liters of solution needed from beaker A
Let B = liters of solution needed from beaker B

Note that we are told liters

Multiply both sides by

And since




liters
Given is


2.4 liters of solution are needed from beaker A
and 3.6 liters of solution are needed from beaker B
check answer:






OK

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If beaker A contains a 15% solution of sulfuric acid and beaker B contains a 20% solution of sulfuric acid, how much from each beaker should be used to make 6 liters of a 18% solution of sulfuric acid?
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EQUATIONS:
Quantity Equation: a + b = 6 L
Active Ingrediant: 0.15a + 0.20b = 0.18(6) = 1.08
----------------
Rearrange for elimination:
15a + 15b = 90
15a + 20b = 108
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Subtract 1st from 2nd to get:
5b = 18
b = 3.6 L (amt. of 15% solution in the mix)
Since a+b=6, a = 6-3.6 = 2.4 L (amt. of 20% solution in the mix)
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Cheers,
Stan H.