Applications of exponential functions: worked problems.

1. What amount of money must be invested today, at 6% compounded annually, if
you need $5000 seven years from today?

2. There are 500 gophers in a field on May 31. On June 20 there are 800. If the
gopher population is growing exponentially, how many are there on June 28?

3. The radioactive gas radon has a half-life of 3.8 days. How much of a 5 g sample
remains after 4.2 days?

4. The population of a colony of Pre-Cal 40S math students grew from 30 to 40
during the period from noon to 2 pm. (These guys really love math!) At what
time will the population be 60?