Exponential Decay Equations

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

• Growth rate

• Growth Factor

• Decay Rate

• Decay Factor

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

• .985

• 1.5

• .015

• 98.5

If something is decaying by 10% every year, the "10%" is called the ______?

• Growth rate

• Growth Factor

• Decay Rate

• Decay Factor

A 2.5% decay rate is what value as a decay factor?

• 97.5

• .025

• 2.5

• .975

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

• between 0 and 1

• greater than 1

• less than 1

• equal to 1

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

A population of 2200 beetles is too large to sustain and decreases in population each month at a rate of 5%. How would you write your decay factor, b?

• -5

• -.05

• .95

• .05

An antibiotic is introduced into a colony of 12,000 bacteria during a laboratory experiment. The colony is decreasing by 14.9% per minute. Which function can be used to model the number of bacteria in the colony after x minutes?

• f(x) = 12000(1 + 14.9)^x

• f(x) = 12000(1 - 14.9)^x

• f(x) = 12000(1 + 0.149)^x

• f(x) = 12000(1 - 0.149)^x

Suppose a culture of bacteria begins with 5000 cells and dies by 30% each year. Write an equation that represents this situation.

• y=5000(0.7)^x

• y=30(5000)^x

• y=5000(1.3)^x

• y=5000x^x