Equation Models and Word Problems

y = 7(1.2)^x

• Growth, because of 7

• Decay, because of 1.2

• Growth because of 1.2

• Decay because of 7

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

• y=8(15,000)^x

• y=15,000(1.08)^x

• y=15,000(0.92)^x

• y=15,000(0.08)^x

Write an equation that models the following situation:
Samantha's hair was known to grow very rapidly. It began at a length of 6 in and grew at a rate of 14% a week.

• y=6(0.14)^x

• y=6(1 + 14)^x

• y=6(1 + .14)^x

• y=6(0.86)^x

The population of Winnemucca, Nevada, can be modeled by P=6191(1.04)^t where t is the number of years since 1990. What percent did the population increase each year?

• 104%

• 4%

• 40%

• 400%

Your shiny new boat cost $7650.  The depreciation for your boat is 14% per year. Estimate the value of your vehicle in 3 years. What is the equation that models this problem?

• y= 7650(.14)³

• y= 7650(.86)³

• y= 7650(1+.86)³

• y = 7650(1.14)³

What is the starting amount for the following function:
f(x) = 3(1/3)^x 

• 0

• 1/3

• 1

• 3

Which of the following functions shows an initial amount of $15 and an increase of 35% each year?

• y = 15(35)^x

• y = 15(1.35)^x

• y = 15(0.35)^x

• y = 35(1.15)^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

_{What is the y-intercept of the line?}

• y = 1/2

• y = 1

• y = -1/2

• y = -1

What is the y-intercept?

• 7

• 0

• 1

• 2