PercenTable

Copy and complete this table without using a calculator!

  480 600 2220 16320
10%
50%
25%
33⅓%
75%
90%

A Mathematics Lesson Starter Of The Day


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Topics: Starter | Arithmetic | Mental Methods | Percentages

  • Transum,
  •  
  • Transum's exciting, fascinating and surprising starters are balanced by this more routine practice exercise. Having said that some pupils will find it a revelation when they learn (from other pupils) tricks for quickly working out these common percentages. A really useful way to spend the first ten minutes of the lesson.
  • Dylan T, Charnwood Primary Lichfield
  •  
  • This was a good starter especially if your target is percentages!
  • Faye D Year 6, Charnwood Primary Lichfield
  •  
  • A good starter as it got my brain working and lots of people found it challenging.

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This starter has scored a mean of 3.2 out of 5 based on 345 votes.


Previous Day | This starter is for 16 October | Next Day

 

% - This is the percent symbol.
Percent means 'out of 100'.

Find 50%:

As 50 is half of 100, then 50% means half. To find 50% of a quantity you need to halve (or divide by two). So 50% of 6 is 3.

Find 10%:

As 10 is one tenth of 100, then 10% means 'one tenth of'. To find 10% of a quantity you need to divide it by ten. So 10% of 800 is 80.

Find 25%:

As 25 is one quarter of 100, then 25% means 'one quarter of'. To find 25% of a quantity you need to divide it by four. So 25% of 20 is 5.

Another way of finding 25% of a quantity is first finding 50% then dividing the result by 2.

Find 33⅓%:

As 33⅓ is one third of 100, then 33⅓% means 'one third of'. To find 33⅓% of a quantity you need to divide it by three. So 33⅓% of 30 is 10.

Find 1%:

As 1 is one hundredth of 100, then 1% means 'one hundredth of'. To find 1% of a quantity you need to divide it by 100. So 1% of 800 is 8.

Find other percentages:

Other percentages can be found by combining some of the techniques mentioned above. Here are some examples:

If you need to use a calculator to check your working. See Calculator Workout skill 3.

Commute

Did you know that if you are struggling to mentally work out 24% of 50 you can switch the numbers round and work out 50% of 24 instead. Finding 50% is very easy isn’t it? You will get the same answer.

Finding a percentage of a quantity is an example of a commutative calculation. Not all operations are commutative. Subtraction certainly isn’t as 10 minus one is not the same as one minus ten.

You can use this trick to improve your ability to do this type of calculation quickly if you find the switch makes it easier.

Practise with 12% of 50, 4% of 25 and 75% of 10.

Answers

  480 600 2220 16320
10% 48 60 222 1632
50% 240 300 1110 8160
25% 120 150 555 4080
33⅓% 160 200 740 5440
75% 360 450 1665 12240
90% 432 540 1998 14688

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