Math CentralQuandaries & Queries


Question from Alan:

Can you add percentages and then divide them by the number of percentages to get the average percentage.
I.E day 1 100% day 2 100% day 3 95% average= 98.3%

is the above possible or is it not done, I have a dispute with a work colleague over this.

many thanks


Suppose you are interested in what percentage of your sales are paid in cash.

On day one you make 2 sales and both are for cash, so that's 100% of your sales on day one are for cash. On day two you make 10 sales and only 1 is for cash, so on day two 10% of your sales are for cash.

Hence on the two days you made 12 sales and 3 were for cash so that's 25% cash sales over the two days. Averaging the 100% and 10% however gives 55%. It is not clear at all what this number represents.


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