percentages using 'boxes'

a ppt is here

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