Download Worksheet 10

Name:_______________________
Period: _________
Worksheet 10-6B
1. In a certain culture the number of bacteria grows exponentially. If 1000 bacteria are
present initially and the amount doubles in 12 minutes, how long will it take before there
will be 1,000,000 bacteria present?
2. The rate of increase of the population of a certain city is proportional to the population
(this means the growth is exponential). If the population in 1950 was 50,000 and in 1980
it was 75,000, what is the expected population in 2010?
3. A culture of bacteria originally numbers 500. After 2 hours, there are 1500 bacteria.
Assuming exponential growth, find how many are present after 6 hours.
4. Strontium-90 has a half-life of 25 years. If 200 kilograms were present originally, how
much will remain after 10 years?
5. A radioactive substance has a half-life of 64 hours. If 200 grams of the substance are
initially present, how much will remain after 4 days?
6. A culture of 100 bacteria doubles after 2 hours. How long will it take the number of
bacteria to reach 3200?
7. How long will it take 100 grams of a radioactive substance having a half-life of 40 years
to be reduced to 12.5 grams?
8. 100 kilograms of a certain radioactive substance decay to 40 kilograms after 10 years.
Find how much will remain after 20 years?
9. If $10,000 is invested at 6 percent interest compounded continuously, in approximately
how many years will the amount have grown to $15,000?
10. If $5,000 is invested at 5.5 percent, compounded continuously, approximately how long
will it take for the amount to double?