Name: Sally Who is asking: Other Level: Middle Question: If 20% of 100 is 80, then why is the percentage difference between 80 and 100 25%. Hi Sally, Percent means per one-hundred so 20% of 100 is  20/100 x 100 = 20. Likewise 20% of 60 is  20/100 x 60 = 12. The second part of your question raises another problem. When you ask a percentage question you need to ask percentage of what. When you say the difference between 80 and 100 is 25% you need to say 25% of what. Consider this example. You buy an item for \$80 and you want to mark it up to sell it. If you mark it up 25% (that is 25% of what it cost you) then you mark it up  25/100 x \$80 = \$20. and sell it for \$80 + \$20 = \$100. In this example the difference between \$100 and \$80 is 25% of \$80. As a second example suppose that a shop owner has an item which sells for \$100. She decides to put it on sale for \$80, and thus marks it down \$20. In this case she would say reduced by 20%. Here she means that the price has been reduced by 20% of the original price of \$100. I hope this helps, Penny Go to Math Central