Answer:
- 33 1/3 liters of 30%
- 16 2/3 liters of 45%
Step-by-step explanation:
Let x represent the liters of 45% solution needed. Then the amount of HCl in the mix is ...
0.45x +0.30(50 -x) = 0.35(50)
0.15x = 0.05(50) . . . . . simplify, subtract 0.30(50)
x = (0.05/0.15)(50) = 50/3 = 16 2/3 . . . liters of 45% HCl
33 1/3 liters of 30% and 16 2/3 liters of 45% HCl are needed.
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<em>Comment on the solution</em>
You may notice that the general solution to a mixture problem of this sort is that the fraction of the mix that is the highest contributor is ...
(mix % - low %) / (high % - low %) = (.35 -.30) / (.45 -.30) = .05/.15 = 1/3
We're going to "cut" the repeating part here in a few steps. First, we're going to put the number in a variable:

Next, to get rid of the negative, we can multiply either side by -1 to get

Now, we won't actually use this -x directly; instead, we want to create two new values, one by multiplying either side by 10:

and the other by multiplying either side by 1000:

Next, we can get rid of the repeated part of the number by subtracting -10x from -1000x:

And finally, we can divide either side of the equation by -990 to find that

It would be smarter to buy it for 3.39 because you will spend money on gas drive Ig to the other store and you will spend more money