Growth Decay Equations

The function y = 24,220 (0.85)^x represents Mr. Bittle's investment in the stock exchange where x is measured in months.

Which statement is NOT true.

• Mr. Bittle loses 85% of his investment monthly

• Mr. Bittle initially invested $24,220

• Each month Mr. Bittle loses 15% of his investment

If something has a 1.5% decay rate, the decay factor is ______.

• .985

• 1.5

• .015

• 98.5

The following function represents a bank account. 
g(x) = 200(1.25)^x
What was the initial dollar amount put in the bank?

• $200

• $1.25

• $0.25

• $2.00

Write the equation that represents the table below:

• y=1/2(4)^x

• y=2(4)^x

• y=4(2)^x

• y=4(1/2)^x

Some banks charge a fee for a savings account that is left inactive for an extended period of time. The equation y = 5000(0.98)^x represents the amount remaining, y, of one account that was left inactive for a period of x years. What does the number 5000 represent in this situation?

• fee charged for an inactive account

• percent of money in the account after x years

• amount of money in the account initially

• amount of money in the account after x years

The function f(x) = 12,500(0.89)^x models the value of a car x years after its purchase. Which statement is true about the value of the car?

• The value is decreasing at a rate of 11% per year.

• The value is decreasing at a rate of 89% per year.

• The value is increasing at a rate of 11% per year.

• The value is increasing at a rate of 89% per year.

The function f(x) = 24500(0.84)^x models the population of a town t years after 2008. What rate is the population of the town decreasing each year?

• 24.5%

• 75.5%

• 16%

• 84%

The value of a car is $15,000 and depreciates at a rate of 8% per year. What is the decay factor?

• ^0.08

• ^1.08

• 0.92

• 8

If something has exponential decay, the "b" value is _____?

• between 0 and 1

• greater than 1

• less than 1

• equal to 1

Genevieve deposited $400 into her bank account. The equation A(t) = 400(1.07)^x can be used to calculate the value of her money after t years. What is the annual interest rate she is earning on her deposit?

• 0.07%

• 1.07%

• 7%

• 10%