Mixture problems

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Mixture problems are popular with GMAT preparation software. We are going to go through some questions of this kind in order to help understand how to solve these problems.

A convenient way of solving a mixture problem is filling in the table of a certain kind that can be drawn in a couple of seconds during the actual GMAT. Here is an example.

{{#x:box| After adding 50 ounces of water to 30 ounces of a strong acid solution a chemist got the 60% acid solution. What was the original percentage of the acid in the solution? }}

At first we need to recognize what exactly happened. There was some amount of acid solution (30 ounces). Then 50 ounces of water were added to the original solution. Note that water is the 0% acid solution, i.e. it does not have any acid in it. As a result, the chemist got the 60% acid solution. Thus, the chemist obtained 80 ounces of 60% acid solution. We need to know what was the original concentration of acid in the solution.

In order to construct an equation, we will fill in the following table with the data from the question stem. will stand for the original concentration. All percent values are to be converted to decimals for convenience purposes.

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