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Any tips on how to calculate

Dario asked on Sep 17, 2018 - 4 answers

I have problems getting a decent score in the hard section of the "percent" exercises in the Mental Math tool here on the site.

Any tips on how to solve this kind of complex operations?

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Wouter replied on Sep 18, 2018
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Another little tip is to practice with multiplications, rather than divisions. It seems to be easier on the brain.

E.g. 30% of 7 is easier done this way:

1) 7 x 30 = 210

2) Divide by 100.

Elias
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replied on Sep 17, 2018
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Practice, practice, practice...

Also, there are some shortcuts I find useful:

  • 90% of X - just divide X by 10 and subtract from X.
  • x% of 1xx - maybe easier to take (x% * 100) + (x% * xx)
  • 20 / 40 / 60 / 80% of 65 / 75 / 85: Take 20 / 40 ... % of 70 / 80 / 90 and subtract 1 / 2 / 3 / 4. So 40% of 65 = 40% of 70 - 2 = 28 - 2 = 26
Alessandro
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replied on Sep 18, 2018
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All good tips below. Ultimately it comes down to personal preference. My tips for dealing with percentages (especially complex ones): think of everything in terms of divisions of 10 and 2 --> i.e. almost any percentage, you can reach by dividing your initial number by 10 or by 2

Example - 37.5% of 460:

- 30% =3*10% = 46*3= 138

- 5% = 23

- 2.5% = 11.5

37.5% = 138+23+11.5 =172.5

Hope this helps!

Alessandro

Vlad
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replied on Sep 17, 2018
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Hi,

Simply learn the division table up to 1/11 (i.e. 5/6 = 83.3%). It will help you calculate any percentage problems

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