these are teacher's notes about using a 'boxes' approach to solve a lot of percentages questions
this approach is also identified in the ratio resources
all percentages questions are the same
- you have four bubbles
- the question gives you two numbers
- a third number is 100
- this enables you to find the fourth
for an age this has been done by cross multiplying (e.g. ancient Chinese)
I prefer not to...
you get from one bubble to another by multiplicative methods
not by adding or taking
I prefer to use two steps (rather than one - the multiplier)
the default being the 'unitary' method: divide by the bubble you are coming from (to obtain 1) and then multiply by the number you are heading towards
sometimes, where there is a convenient common factor, this can be used as a 'stepping stone' - rather than 1
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