15% of 15% of 15% of 500 is 1.6875. 45% of 500 is 225. The difference between both numbers is that 225 is much larger than 1.6875. In fact 225, is 133 1/3 times larger than 1.6875. The more you repeated 15% of a number, the smaller it got, compared to 45% of the number, where it was larger than that number you kept reducing by percentages.