Practice with
Applications of
Exponential Functions
Topic Index | Algebra2/Trig Index | Regents Exam Prep Center

Solve the following problems dealing with exponential functions.
You may want to have your graphing calculator handy.
(Each solution method shown is but one possible approach to the answer.)


Diego decided to invest his $500 tax refund rather than spending it. He found a bank that would pay him 4% interest, compounded quarterly.  If he deposits the entire $500 and does not deposit or withdraw any other amount, how long will it take him to double his money in the account?





The half-life of carbon-14 is known to be 5720 years. Doctor Frankenstein has 300 grams of carbon-14 in his experimental laboratory.  If untouched, how many of the 300 grams will remain after 1200 years?




Your brother tells you a secret.  You see no harm in telling two friends.  After this second "passing" of the secret, 4 people now know the secret (your brother, you and two friends).  If each of these friends now tells two new people, after the third "passing" of the secret, eight people will know.  If this pattern of spreading the secret continues, how many people will know the secret after 10 such "passings"?




The radioactive element polonium-210 has a half-life of 138 days.  If you have 100 micrograms of polonium-210, how much will remain after 60 days?



The number of wolves in the wild in the northern section of the Cataragas county is decreasing at the rate of 3.5% per year.  Your environmental studies class as counted 80 wolves in the area.  After how many years will this population of 80 wolves drop below 15 wolves, if this rate of decrease continues?