Using different methods to solve the same problem is fun and can give you better understanding of some concepts. Let's say, you are calculating 50 - 5. 50 is 200% of 25, 5 is 20% of 25, 200% - 20% = 180%, 25 * 180% = 45. Now, understanding why using percentages gives the same result as simple subtraction is not obvious at all and requires some heavy abstract thinking.