Interesting growth rates
Watch those digits
Percentages need careful watching:
If you boost sales by 10% a year for 10 years, the overall increase will be 160%, not 100%.
If you boost prices by 50%, and then cut them by 50%, they end up 25% below where they started from.
If your credit card company charges you 3.5% a month interest, this grosses up to a penal rate of over 50% per annum.
Of money, percentages and proportions
We are all familiar with percentages and proportions from everyday dealings with money. Nevertheless, I am going to state the obvious:
Proportions. One cent is 0.01 of a dollar.
Percentages. One cent is one percent (1%) of a dollar.
If something grows by x%, it has to shrink x / (x + 100) to return to the starting point.