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Getting' Shmoopy with it...

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William is diluting a 100% solution with water to create a solution that is 60%.

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If he has 30 milliliters of the 100% solution,

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how much water does he need to add to make the 60% solution?

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And here are the potential answers...

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This problem wants us to find the amount of water that William needs to make a 60% solution.

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To do so, we also need to know how many total milliliters of solution William will have

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when he's done. Let's assign variables to the two unknowns,

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we'll call the amount of water William needs to add w,

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and the total amount of solution x.

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Since there's a lot of information, let's make a chart of what we know.

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The x milliliters of 60% solution is the result of adding the 100% solution and the water.

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Our equation can be set up as 30 times 100% plus 0% times w equals 60% times x.

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That's the same thing as 30 times 1, or 30...equals 0.6x

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We solve for x by dividing both sides by 0.6, and we get x equals 50.

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So 50 milliliters is the total amount of 60% solution

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that William will have at the end of the day.

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...the amount of 100% solution plus the amount of water put in should total 50 milliliters.

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Our equation is 30 + w = 50.

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The w, the amount of water William needs to add, is 20 milliliters...

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...which makes D 100% of this problem's solution.

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