Well no you are not changing anything, not even the baseline.Another thing about percentages is that you are changing the baseline.
an increase from 100 to 120 is a 20% increase,
A decrease from 100 to 80 is a 20% decrease.
Now you have moved the baseline.Wait for it —- ——- An increase from 80 to 100 is a 25% increase.
So 80 and 100 two numbers from one to the other is 20 percent one way but is 25% the other way .
The simple fact is 20% of 100 ≠ 20% of 80 and 10% of 100 ≠ 10% of 110.Therefore if you start from 100 then keep adding 10% at every step then you get to the end of your series of steps then decrease by 10% for the same number of steps you get two confusingly different answers.
Whether you're adding or subtracting makes no difference to the baseline, IE: 100+20% = 100+20 & 100-20% = 100-20.
It makes no difference adding the % then discounting or vice versa, IE: 100+20%-10% = 100-10%+20%. In that calculation the baseline does move for the second element IE it moves from 100 to 120 in the first instance and to 80 in the second,
One of my favourite numerical quiz questions is along the lines of: A TV costs £100 +20% VAT during a sale the price is reduced by 20%, how much will it cost. It's amazing listening to the mistakes in the teams discussions.
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