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Why and how to calculate percentages of whole numbers

January 23, 2012 by Simon 32 Comments

There are a few ways of learning how to calculate percentages of whole numbers ..

.. although this video shows how to calculate percentages by converting to fractions and then cross division.

‘Percentage’ means ‘out of 100.’  Therefore we can use the idea of ‘equivalent fractions’ to make the numbers smaller and easier to deal with.

So 12% is exactly the same as 12/100; which is equivalent to 6/50 or 3/25.

Any number can be written as divided by 1.

So 50 is the same as 50/1 – we then use cross division to make a calculation.

The key points to remember are:

  • ‘whatever we do to the top, we have to do to the bottom.’
  • don’t forget that ‘of” always means ‘multiply.’

Finally, not all questions require you to answer as a decimal – it’s perfectly OK to leave as a fraction (providing you make sure it’s as small as possible).

This is a popular method that is taught in schools:

Why are percentages important?

Most of everyday life involves percentages, usually as a comparison.

For instance 30% discount seems a much better deal than 10%… or does it? (you really need to work out the actual price you pay).

Generally we tend to mix and match between fractions and percentages. Although it’s the same thing, 30% seems a lot friendlier than a discount of 3/10ths !

Watch the videos on YouTube:

https://www.youtube.com/watch?v=L_0T-WPQH18

https://www.youtube.com/watch?v=zM1DmuKLwkw

https://www.youtube.com/watch?v=j7VMJSTw1tE

[easyazon_image align=”none” height=”160″ identifier=”1447980204″ locale=”UK” src=”https://www.3minutemaths.co.uk/wp-content/uploads/2016/04/51PqY1BYYTL.SL160.jpg” tag=”matwra-21″ width=”118″]

Comments

  1. Sean Dempsey says

    July 16, 2015 at 9:24 pm

    your a lifesaver

    Reply
  2. ThealmightyFlinson says

    June 10, 2015 at 12:37 pm

    if you don’t simplify would it be correct?

    Reply
  3. gaia Hill says

    May 25, 2015 at 3:55 pm

    Thank you:)

    Reply
  4. sukr bait says

    May 21, 2015 at 3:35 am

    Why not just leave it as 50/200x 100= 25? Why add another whole step?

    Reply
  5. Andrew Adamian says

    March 16, 2015 at 11:51 pm

    THANK YOU SOOO MUCH! Really appreciate it!

    Reply
  6. red reuben says

    January 8, 2015 at 6:32 pm

    good

    Reply
  7. LetsLearnArabic says

    December 19, 2014 at 3:17 pm

    You’re an awesome teacher, yeah I totally forgot how to do this also I
    guess as a suggestion you could have simplified the end i.e. 36/5 by doing
    36/10 then multiplying it by 2? I guess if your math is decent then long
    division should be fine but I find it easier to do it that way?

    I guess the suggestion is for your students, seeing your math is really
    good.

    Reply
  8. andrejustin bayarong says

    December 14, 2014 at 4:59 am

    Thank you sir Simon Deacon for helping me answering my Ass.

    Reply
  9. Jiyat Singh says

    November 1, 2014 at 2:20 am

    thank you

    Reply
  10. Donal Gray says

    September 22, 2014 at 2:12 am

    Just letting you know that your final equation (37% of 600) was off by a
    count of 60. You said 3 times 10% but only added it up to 120 rather than
    180. Perfect bar that wee slip of the tongue.

    Reply
  11. Stephanie Anne says

    July 28, 2014 at 10:50 am

    You can do canceling. Example you divide 20 to 10. You can see there’s one
    0 to 10 so your just gonna cancel how many zeros are there? Is it right?

    Reply
  12. Nicola Bean says

    July 20, 2014 at 3:15 pm

    Brilliant, absolutely brilliant just what I needed thankyou so much 🙂
    Great help

    Reply
  13. Tech Bliss says

    June 16, 2014 at 9:57 pm

    best method, best way no doubt :D.
    Number and Algebra – completed
    Geometry and Measure – Completed
    Statistics and Number – Tuesday 17th June 2014

    The statistics and numbers is the one i fear very badly ): I will not do
    good and it will reduce my grade by 50% lol

    Reply
  14. Usman Ikhlaq says

    June 12, 2014 at 10:33 pm

    Excellent. Good for last minute revision!

    Reply
  15. Sage art says

    May 19, 2014 at 6:45 pm

    U cud of just cancel out by 20 in the first place and 60 would have become
    3 and the 100 would become 5 .

    Reply
  16. Johnny Bramble says

    May 12, 2014 at 5:18 pm

    Thank you soooo much I am only in year 4 but I got level 5 questions during
    the holidays and percentages was one of them

    Reply
  17. Johnny Bramble says

    May 12, 2014 at 5:18 pm

    Thank you soooo much I am only in year 4 but I got level 5 questions during
    the holidays and percentages was one of them

    Reply
  18. weelouisexo says

    April 28, 2014 at 12:08 am

    Can you tell me as I cannot find it anywhere.. How do you work out the
    percentage difference between a number? Preferably on a calculator. For
    example, calculate the difference between 5.0 and 5.4 as a percentage.

    Reply
  19. deerashini deerashni says

    April 16, 2014 at 1:16 pm

    Thank u sooo mch…I forget it cause my exam was going tonbe the follow day
    soo I got stree and forget abt it

    Reply
  20. Ziheng Liao says

    March 25, 2014 at 11:24 am

    Better than my teacher

    Reply
  21. Dudeloo Kanavos says

    February 26, 2014 at 8:18 pm

    this is a bullsh*t method

    Reply
  22. Rasmus Haycraft Mee says

    January 19, 2014 at 7:54 pm

    Thanks ALOT. By the looks of things I am going to be checking out quite a
    few of your vids

    Reply
  23. sakina221 says

    December 25, 2013 at 3:12 pm

    Thanks ur videos are really helping me in order to revise for my gcse mock
    exam as I’m doing foundation for me to do higher have to pass foundation
    I’m really grateful you explanations are much easier to understand

    Reply
  24. Simon Deacon says

    October 27, 2013 at 11:59 pm

    Please post, pin, tweet, like or subscribe!

    Reply
  25. Simon Deacon says

    October 27, 2013 at 11:57 pm

    Please post, pin, tweet, like or subscribe!

    Reply
  26. Ajandeen Ali says

    September 17, 2013 at 2:23 am

    thank you Mr you really helped me with this and thought me a very simple way in working out percentages ….. thanks alot

    Reply
  27. Awake Drake says

    August 2, 2013 at 10:53 pm

    not bad at all-

    Reply
  28. Simon Deacon says

    June 11, 2013 at 11:29 am

    Thanks – really appreciate comment 🙂

    Reply
  29. Randy Munguia says

    June 11, 2013 at 6:27 am

    Great Vid!

    Reply
  30. Simon Deacon says

    June 8, 2013 at 12:39 am

    Thank you 🙂

    Reply
  31. Randy Munguia says

    June 7, 2013 at 11:57 pm

    Excellent video!

    Reply
  32. Lord Razor says

    May 20, 2013 at 9:51 pm

    your amazing

    Reply

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