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How Much Is Seventy Percent Off? (Calculating Percentages in Your Head)

Updated on June 07, 2016
SusanDeppner profile image

Susan enjoys answering questions and helping her readers solve problems while learning more about education, business, and other fun topics.


Joined: 2 years agoFollowers: 372Articles: 27

Stuck on a Percentage Problem?

Seventy percent off is almost always a bargain if you're shopping. But it's good to know how to calculate percentages in your head (or even on paper) so you'll know for sure if you're getting a good deal. And if you're taking an important math test, well, you really need to know how to work with percentages.

In this article, you'll learn how to calculate percentages, including seventy percent off, and a few more math tricks you can do in your head. You'll also find out where you can learn more about math so the next time you come across a sale or a percentage problem you'll be able to amaze your friends (and yourself) by figuring out the solution, calculating percentages faster than a speeding shopping cart on your own, in your head.

No matter what your age, if you have a working knowledge of basic math you can learn math tricks and shortcuts to make calculating percentages and doing other mental math easy.

Watch This Video

In our explanation, we'll be using some of the information found in this video. It's just over 10 minutes long, but that will be time well spent to review or learn the basics of percentages, then practice to become familiar and comfortable with using this method of mental math.

To learn more than just percentages, take a look at more math videos from tecmath on YouTube.

The Easy Solution in Pictures

Click thumbnail to view full-size
(In this case, it's easier to do the math with the 3 than the 7.)(You saw this in the video. Remember?)(This is easy math, but the method works the same way with harder numbers.)(We're pretending to work with money because that makes the figures easier to visualize.)
(In this case, it's easier to do the math with the 3 than the 7.)
(In this case, it's easier to do the math with the 3 than the 7.)
(You saw this in the video. Remember?)
(You saw this in the video. Remember?)
(This is easy math, but the method works the same way with harder numbers.)
(This is easy math, but the method works the same way with harder numbers.)
(We're pretending to work with money because that makes the figures easier to visualize.)
(We're pretending to work with money because that makes the figures easier to visualize.)

How did you feel about math when you were a student?

See results

Here's How to Calculate Seventy Percent Off in Your Head

Here's the long explanation, in words. There's actually two ways to do it.

Did you watch the video above? If you did, you've probably already solved your 70% off problem. If not, here's our explanation.

First, make sure you're asking yourself the right question. If you need to know, "What's 70% off?" then what you're actually asking yourself is, "What's 30% on?" Let me explain.

Let's say we're working with $250. We want to know what's 70 percent off of $250. Well, do we really want to know how much we're going to take off or how much is left after we remove that 70 percent?

To calculate 70% of $250, use the method described in the video above to figure 50% + 10% + 10% (which add up to 70%) because those numbers are really easy to work with. So, 50% (or half) of 250 is 125, then we move the decimal back one place to determine 10% of 250, which gives us 25.

So we get 125 + 25 + 25 which equals 175. So, now we know that 70% of $250 is $175. But we want to know what is 70 percent OFF of $250, so to get that answer we subtract $250 - $175 which equals $75. Not difficult math, but there's an easier way.

Since we know that when we subtract 70% from 100%, we have 30% left, the amount we're actually looking for is 30% of $250. (In other words, we're saving 70% but spending 30% and we really want to know how much we're going to spend.) So why not calculate that in the first place? Here's how we do it:

To calculate 30% of $250, think 10% + 10% + 10% adds up to 30%. We move the decimal back to the left to get our 10%, so 25.0 is 10%. Then we either add 25 + 25 + 25 OR we multiply 25 x 3. In either case, we get our answer, $75. That's much quicker and easier than working with the 70 and having to take an extra step to subtract.

So the bottom line of "70 percent off of $250" is the same as "30% of $250." 3 x $25 = $75. That's the sale price and wow, what a bargain!

What is a percent, anyway?

Percent simply means parts out of hundred.

Per - cent

Parts out of - one hundred

One penny out of a dollar is 1 percent.

Using a Calculator

There's more than one way to calculate a percentage. If you have a calculator, you'll need to structure the problem a little differently from the way we did it above.

To calculate seventy percent off on a calculator, think "250 minus 70% equals what?"

Using the calculator, enter the starting number (250 in our example), then the minus sign, then 70 followed by the % key, then the = key to get the answer.

250*70%=175

More Mental Math Videos

I like this teacher. His voice is kind and his math methods are magical!

You'll need to know how to multiply when you calculate percentages and his videos will help teach you shortcuts to make multiplication quicker. There's also a subtraction video here. You'll love the time-saving methods for working with numbers that you'll learn here.

© 2014 Susan Deppner

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    • SusanDeppner profile image
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      Susan Deppner 6 months ago from Arkansas USA

      Shyron, I'm glad you were able to get back on HP and watch the video. Thanks for taking that extra step and letting me know. Hope you found the video helpful, too! Appreciate your visit and your comment. Have a blessed day!

    • Shyron E Shenko profile image

      Shyron E Shenko 6 months ago

      Susan, maybe it is a problem with my computer, I got out of HP and when I came back I could watch the video.

      Blessings.

    • Shyron E Shenko profile image

      Shyron E Shenko 6 months ago

      Hello Susan, I really like this, math was not my best subject in school. I could not watch the video in this hub it is not there. I think it has something to do with the nit picking niche.

      Blessings my friend

    • SusanDeppner profile image
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      Susan Deppner 8 months ago from Arkansas USA

      Thank you very much for the feedback, Sunlkunnoth. Appreciate it!

    • Sunilkunnoth2012 8 months ago

      Hi, I loved this post which contains excellent information. It is helpful too. Thank you for your great job.

    • SusanDeppner profile image
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      Susan Deppner 8 months ago from Arkansas USA

      Carol, I am so happy to know that this information was helpful for you and your daughter. Thrilled you could use it! Thanks so much for the comment.

    • Carol Morris profile image

      Carol Morris 8 months ago

      This was the perfect hub for me to come across today. I've been working with my daughter on her math and I really need to use these resources. Thanks for saving me with this information today!!

    • SusanDeppner profile image
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      Susan Deppner 15 months ago from Arkansas USA

      Yes! Coupons are a good example of when we need to know how to calculate percentages in our heads to see if we're really saving money. Thanks for stopping by, Rabadi, and for the follow! (Following you back!)

    • Rabadi profile image

      15 months ago from New York

      Very useful hubs I often get those coupons in the mail with 20 or 25 percent off on a certain amount it's great to have this trick in your head to help you count, great hub, I am following you :)

    • SusanDeppner profile image
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      Susan Deppner 17 months ago from Arkansas USA

      You're welcome, Rachel, and I hope you'll be able to use the tip. Thanks so much for the vote, your kind comment, and definitely the blessings!

    • Rachel L Alba profile image

      Rachel L Alba 17 months ago from Every Day Cooking and Baking

      Hi Susan, I really like that idea of figuring out the 30% first instead of the 70%. It works for other percentages too. I was the worse in math in school, many many years ago. lol So thanks for this tip. I voted up and useful.

      Blessings to you.

    • SusanDeppner profile image
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      Susan Deppner 18 months ago from Arkansas USA

      I know what you mean, Lorelei! We each have our strengths and definitely our weaknesses, especially when math is involved. Thanks for stopping by!

    • Lady Lorelei profile image

      Lorelei Cohen 18 months ago from Canada

      Math has always been a terror for me. English for me please. ;)

    • SusanDeppner profile image
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      Susan Deppner 20 months ago from Arkansas USA

      Thank you, Akriti!

    • SusanDeppner profile image
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      Susan Deppner 20 months ago from Arkansas USA

      Thanks for sharing, Sunil. Appreciated!

    • Akriti Mattu profile image

      Akriti Mattu 20 months ago from Shimla, India

      This my friend is such an interesting post for so many shopaholics. voted up :)

    • sunilkunnoth2012 profile image

      Sunil Kumar Kunnoth 20 months ago from Calicut (Kozhikode, South India)

      Very interesting and useful hub. Hence shared.

    • SusanDeppner profile image
      Author

      Susan Deppner 21 months ago from Arkansas USA

      Ah, good point, Rangoon House. I hadn't thought about that aspect, but certainly it would be very important to be able to do at least a rough calculation when dealing with foreign currencies. Thanks so much!

    • Rangoon House profile image

      AJ 21 months ago from Australia

      Thank you for this Susan - I need it with the Australian dollar around the percentage of the US dollar at the moment.

    • SusanDeppner profile image
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      Susan Deppner 21 months ago from Arkansas USA

      I like that approach to math, shilemarie78. A positive attitude really does make a difference. Thanks so much for the visit and the thumbs up!

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