Urgent math problem! Why should division be used for currency appreciation and depreciation, and for improving and reducing industrial labor productivity? For example, if 20 yuan appreciates by 20%, it will cost 20( 1+20%). ... A 20% appreciation in 20 yuan means that the amount of money needed has changed, and the same money can do more things, so it needs 20÷( 1+20%). On the other hand, if the depreciation is 20%, that is to say, the same money can't do so many things, and it will take 20÷( 1-20%).