Working with Percents: Percents to Decimals

How do you turn percents to decimals so that they can be more easily used in your math equations? Or how do you make a percent into a fraction? This video lesson will teach you these fundamentals of working with percents. And once you have this lesson down, check out our other video lessons on percents and ratios.

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Transcript: Working with Percents

What is 55% of 400? Or 240 is 30% of what number? Now these could be test problems in and of themselves. They certainly would be things you might have to do in the context of a larger problem. So in this video I will show a few ways to tackle questions such as this.

Percents To Decimals

The first really big idea is percents as multipliers.

The decimal form of a percent is called the multiplier for that percent. This is because we can simply multiply by this form to take a percent of the number. So when we’re using percents as multipliers, here are the basic things to remember. Remember “that is” means equals.

Remember “that of” means multiply. Change any percent to the multiplier form and replace unknowns with a variable. So for example what is 80% of 200? The what, (the unknown) that will be x, is that becomes equal, 80%, that will become the multiplier 0.8. And then we’ll multiply that of times 200.

So translating that sentence into math, we get 0.80 times 200, we multiply out, we get 160.

Similarly 240 is 30% of what number? 240 equals 0.3, 30% is 0.3 times and then what number, x? So translating to math and of course we divide, move the decimal place over and divide out, we get 800.

Now the second way to use this, is in questions where we have to find the percent.

So 56 is what percent of 800? So here, we set things up again. 56 equals x times 800. We’ll have to remember that x, of course, is a multiplier, so we divide out. We can cancel the factor of eight, we get 7 over 100, which is 0.07. That’s a multiplier, which corresponds to 7%.

Percents and Fractions

Finally, percents and fractions. Use this approach only if the percent is a very easy fraction, for example 1/2 or 1/4. So if it’s a very easy fraction, then sometimes it’s easier to change things to a fraction. So we get the question, what is 75% of 280?

Well, it’s much easier just to remember 75%, that’s 3/4. What’s 3/4 of 280? Cancel the 4’s we get 3 x 70, which is 210. Here’s some practice problems. So, pause the video and practice these now. Here are the answers.

Summary: Percents to Decimals

So in summary, use percents as multipliers, that is their decimal form and the method for solving the simple percent problems. Using the same method to find an unknown percentage. So the unknown would be the percentage of itself, will get a decimal value, we’ll have to remember that is the multiplier form, the decimal form of a percent. And then we can use certain fraction shortcuts for percents

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Author

  • Mike MᶜGarry

    Mike served as a GMAT Expert at Magoosh, helping create hundreds of lesson videos and practice questions to help guide GMAT students to success. He was also featured as "member of the month" for over two years at GMAT Club. Mike holds an A.B. in Physics (graduating magna cum laude) and an M.T.S. in Religions of the World, both from Harvard. Beyond standardized testing, Mike has over 20 years of both private and public high school teaching experience specializing in math and physics. In his free time, Mike likes smashing foosballs into orbit, and despite having no obvious cranial deficiency, he insists on rooting for the NY Mets. Learn more about the GMAT through Mike's Youtube video explanations and resources like What is a Good GMAT Score? and the GMAT Diagnostic Test.

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