1. How quickly will a country, growing at 2% a year, double its income? What about a country growing at 4% per year? How would that compare with a country growing at alternating rates of 0% and 8% per year? (in other words, which country grew faster, a steady 4% per year, or the "unstable" growth country, after 20 years).

2. Suppose a country's per capita income is currently growing at 4% per year. Then it adds an additional percentage point to its population growth rate for the next twenty years, but overall income continues to grow at the same rate. How much poorer/richer would the country be at the end of twenty years (per capita)? You don't need to solve it out - just show us the equation. But the equation should not include the number "4" - you can simplify this problem.