Activity:

Read the information below and do the three problems that follow. When done put you answers in the drop box with a short explanation of how you did them.

Exponential Growth / Decay

Exponential Functions take the form:

y = abx. Where a = initial investment/payment (y – intercept)

b = rate of return or interest

x = term in cycles (minutes, days, months, etc)

When b > 1 then this is a growth function. When 0 < b < 1 then this is a decay function.
Growth function example

Decay function example

1. You start an account with $500 and an interest rate of 6% compounded yearly. How

much is in the account after 3 years?

a) Exponential growth or decay:

b) Identify the initial amount:

c) Identify the growth/decay factor:

d) Write an exponential function to model the situation:

e) “Do” the problem:

2. You start an account with $2500 and an interest rate of 6.5% compounded yearly. How

much is in the account after 7 years?

a) Exponential growth or decay:

b) Identify the initial amount:

c) Identify the growth/decay factor:

d) Write an exponential function to model the situation:

e) “Do” the problem:

Remember: a) Exponential growth or decay:

b) Identify the initial amount:

c) Identify the growth/decay factor:

d) Write an exponential function to model the situation:

e) “Do” the problem:

3. A newly hatched channel catfish typically weighs about 0.06 gram. During the first 6

weeks of life, its weight increases by about 10% each day. Write a function to model the

situation. How much does the catfish weigh after 6 weeks?