How Much Is Seventy Percent Off? (Calculating Percentages in Your Head)
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
How did you feel about math when you were a student?
Photo: Some rights reserved by The hills are alive
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
COMMENTS: Can you calculate seventy percent off in your head? Do you have a favorite math shortcut to share? Just want to say hello?
Hi to everyone, I have my own way to do this type of calculations. If I have to know how much is 70% of 250 or another number I do like that:
Everyone knows that 10% is 25 so
25*7 =150.
Sorry for my english and thank you for this article. Gratings from somebody who love to do math calculations in head wythout calculator :)
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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!
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.
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
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Thank you very much for the feedback, Sunlkunnoth. Appreciate it!
Hi, I loved this post which contains excellent information. It is helpful too. Thank you for your great job.
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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.
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!!
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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!)
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 :)
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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!
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.
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I know what you mean, Lorelei! We each have our strengths and definitely our weaknesses, especially when math is involved. Thanks for stopping by!
Math has always been a terror for me. English for me please. ;)
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Thank you, Akriti!
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Thanks for sharing, Sunil. Appreciated!
This my friend is such an interesting post for so many shopaholics. voted up :)
Very interesting and useful hub. Hence shared.
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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!
Thank you for this Susan - I need it with the Australian dollar around the percentage of the US dollar at the moment.
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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!
If you think of math as a puzzle or game, then you can approach it with a positive attitude instead of as something that makes you weak-kneed. You've done a good job of explaining how to calculate percentages-off that I'm sure many will find useful. Voted up as "useful."
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Thanks for that, poetryman! Most children don't think math like this is child's play, but I'm glad you think it is. I appreciate the visit and the kind comment!
The 30% remainder trick for the 70% off is very useful. And the fact that you can add up 10% three times makes it child's play!
Vote up for usefulness.
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It can be confusing the first time through, but it makes sense once your mind takes it all in. I can't even imagine dividing by 23, at least not in my head! Happy Easter to you too, Elsie!
Very interesting article, I got lost along the way reading it but I will be back when I'm not so busy, (it easter and visitors coming back for lunch).
The only one I remember when doing GST in New Zealand is 15% - thats multiplied by 3 and then divided by 23, have to do it every three months.
Maybe there's a easier way to do even that.
Hope you are having a happy easter.
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I do that too, PegCole17, and I'm always impressed when cashiers "get it" rather than getting confused! Thanks so much for stopping by.
Doing the math in my head keeps my mind active. I like your explanation of the seventy percent off. I use ten percent a lot since that's so easy to figure and then multiply as needed. I'm one of those people who give the cashier odd change so that I will get back quarters or a five dollar bill rather than four ones and eighty-five cents in coins.
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I agree, Swadhin Kumar, that if we don't use it (math ability) we tend to lose it! Thanks for stopping by!
It is easier to calculate percentages (usual discounts we get at shops) by breaking them to multiples of 10 and 5. Perhaps we all knew it but forgot it because of long dissociation with elementary mathematics. Thanks.
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Glad I could help, Myra. Thanks so much for the feedback!
OMG, Thank you Susan for the refresher course on percentages. I was okay with math but not the greatest, I also have forgotten skills of math by not practicing. If you don't use it you lose it. Again, thank you so much, it's so easy the way you explain it.
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Good, really good math teachers seem to be few and far between, Joan. It takes a gifted person to keep the subject "thrilling." I hope you found something here to enjoy. I really liked the math teacher on the videos.
I was great as a child, but then I had one bad teacher after another, so I gave up on the subject. Later, I had to do maths for Physics, but it wasn't the same, the thrill had gone.
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Thank you for those very kind words, Writer Fox. Parents certainly can be intimidated when it comes to helping their kids with math homework. I hope they find this and find it helpful, too.
So many kids have trouble doing simple math these days because they are so reliant on online calculators. This is very useful information and I hope many parents and teachers will find your article. Enjoyed, voted up and shared!
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It is nice to have an app for that, Sunshine625! I never thought about the letters versus numbers clash. Perhaps you're onto something there... Thanks so much for stopping by (and for the follow!).
I am so BAD with math. Numbers and I never got along well. Possibly numbers are envious of my love of letters. It's a love hate kind of relationship. Luckily with a calculator on my phone I no longer have to use my brain cells to figure out percentages :)
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I'm a visual learner too, Jemjoseph, so that's how I recognized you. :)
Yes, money did come to mind and a teacher once told me that I was a visual learner, how very perceptive SusanDeppner, I'm impressed.
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I definitely agree, Jemjoseph, that the key is in knowing the formula, or at least which formula works for you. Your example makes me think of money. It's easy to divide dollars into quarters, which is where your method starts, I think because it's a very visual process, easy to imagine in your mind. In fact, I think learning styles play a big role in learning math. I'm guessing you're a visual learner. Thanks for your input to the discussion!
Great tips for calculating percentages mentally, the beauty about math is that once you know the right formula getting the correct answer is easy. Sometimes there are other formulas that can be applied to find the right answer, in which case it's a matter of choosing the most efficient method.
To find 70% mentally I usually first find 75 % (divide amount by 4 & multiply answer by 3), then subtract 5% (by finding half of 10%), not very efficient I suppose, but it gets the job done.
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@favored: Thanks, I appreciate that feedback!
Good lesson on the percent process. Math can really be tough sometimes and it's nice to see it explained so clearly.
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@Coffeebreaker: Awesome! It really is fast once you have the concept, which is simple. I think we depend on calculators too much these days, don't you? Thanks so much for commenting!
HI Susan! My mom never bothered helping me with school work,but for 2 times that I still remember this day... how to add 9's and do percent breaking down to 10% times however much and 5% is half of the 10%. I can almost do it faster than someone using a calculator!
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@kimberlyschimmel: Yes, unfortunately. I can see where an excited customer would get confused with two 50 percent off offers combined - unless she did the math! Thanks for the visit!
Almost nobody seems to understand percentages any more. I know a retail worker who had an irate customer insisting that an item that was 50% off with an additional 50% off the sale price was free. Logic and math are lost arts for most of the population, unfortunately.
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@ologsinquito2: Oh, my, I absolutely agree with you. I think our brains are just so full of information, there's hardly room for calculations! :)
This is good to know. It takes me longer to calculate anything, now that I've reached middle age.
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@EnthusiasmMadame: I agree - some people seem to have a math phobia. I have a kiddo who was like that. He got to eighth grade and said he'd had enough of math, that he wasn't going to be a math teacher so why should he spend time with algebra? This is the son who graduated college with a 4.0 average, so obviously he got past it. :D Thanks so much for stopping by and for your comment!
I can calculate most percentages off in my head. I loved math in school, however several family members including my daughter had a horrible time with math. I think people make it more often than it needs to be much of the time.
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@shatabdi85: Lots of ways to do the calculation, shatabdi85, thanks for your contribution! I think the key is to not be afraid of math and to break it down into steps. Thanks so much for commenting!
The method show over here is good & effective. Another easy method would be multiply the number with .7 to calculate 70% of a number.
Like (i) 70% of 80 is 80*.7=56
(ii) 70% of 25 is 25*.7=17.5
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@TerriCarr: Great explanation of your method, which works on the same principle of breaking down the percentage into easy chunks. I agree about the teacher, too. My son reviewed algebra on YouTube and learned it so well, he CLEP'd all of his college math classes. What a great education we can get just from the right video teacher!
I use similar tricks to calculate things quickly. With the 70% off 250 problem, I would probably say, well 50% is 125, and I need to take off another 20 %, so I'd do 10% is 25, and times 2 is 50....so 125 - 50 = 75.
Love the Aussie accent and friendliness of the guy in the video. Just having a friendly, relaxed teacher would probably help a lot of math phobic people.
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@asereht1970: Sometimes math does seem to take on a personality of its own! Glad you enjoyed the tip.
Thank you for this wonderful tip. I guess I'm better with percentage than I am with fractions. Still, I'm not that good in Math. I don't like it and I believe it doesn't like me to.
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@BenjaminFrancs: Percentages aren't so bad once you understand how they work. Then they're easy! Glad you learned to like them. Thanks so much for the great comment!
Thanks, this wonderful. I had a problem with percentages until last semester of college. Now they are my favorite!
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@Merrci: Thanks, Merrci. I hope so, too.
What a great lens! Very interesting topic too. I'm always so surprised when people can't do 10 or 20%. Hope this helps many.
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@Ruthi: I'm proud of you, Ruthi! I can, too, but not as fast as I used to do it!
As much as I don't like math I am happy to report that I can calculate percentages in my pretty little head quite easily and correctly!
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