MBF 3C
Exponential Growth & Decay TIPS Assignment
Name: _____________________
1. Fill in the blanks. (8)
Growth / Decay
Growth
Growth/Decay Rate r
28%
_____
35
b
0.95
Decay
50%
Growth
3.7%
1.15
Decay
4½ %
2. You use a natural weed killer that promises that the percent of weeds, N, will decrease
according to N=100(0.93)t after t days.
a) What is the initial percent of weeds? (1)
b) What is the rate of decay (as a percent)? (1)
c) What percent of weeds will remain after 1 week? (3)
3. You invest in a mutual fund that promises a return of A = 5000 (1.12)n where A is the amount in
your account after n years.
a) What do the 5000 and 1.12 tell us about the investment? (2)
b) How much will you have in your account after 15 years? (3)
c) Estimate how long it will take for your investment to double. (3)
4. The population of a town is 20 000. It is growing at a rate of 1.5% per year. What will the
population be after 5 years? (4)
5. A patient is administered 500mg of a certain drug. The amount of the drug decreases by 30%
every 3 hours. How much of the drug remains after 12 hours? (4)
6. A bacterial culture has a starting population of 7500. It increases by 30% every 6 hours.
a)
How many bacteria will there be after 3 hours? (4)
b)
Estimate how long it will take until there are 15 000 bacteria. (2)