This percentage trick is so easy – but you probably don’t know it…because, let’s face it, you were not paying attention in school when the teacher told you!
That’s OK – youtube and tecmath has your back – with this, the easiest percentage trick you were EVER taught in school!
msamba 
I had high hopes, but it only works if one number can be divided by 25 … 😦
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I’d never thought of what it meant for the operation to be valid in either direction before (for example 80% of 30 [15] is the equivalent of 30% of 50 [5 is 10% of 50] or 20% of 25 [5] is equivalent to 25% of 20! It works better for me when the percentage is also familiar as a fraction though it was still true of 44% of 150 [66].
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But going after his examples, should not 80% of 30 give the same as 30% of 80? It does, 24. But it is only easy to calculate, if one of the numbers is divisble by 25, because then we have 1/4, 1/2 etc.
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