Unit 7 Review

Which the following graphs shows an exponential decay equation?

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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?

• 4%
• It doesn't say
• I don't know
• 400%

You bought a Boston Whaler in 2004 for $12,500. The boat's value depreciates by 7% a year. How much is the boat worth in 2012?

• $11625
• $6994.77
• $21,477
• $875

An adult takes 800 mg of ibuprofen. Each hour, the amount of ibuprofen in the person’s system decreases by about 29%. How much ibuprofen is left after 6 hours? 

• 101
• 102
• 103
• 104

Denise has $80 in a savings account that earns 10% interest, compounded annually.
To the nearest cent, how much will she have in 3 years?

• $106.48
• $26.48
• $8 
• $104

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

• y = 15(35)^x

• y = 15(0.35)^x

• y = 15(1.35)^x

• y = 35(1.15)^x

The number of mosquitoes at the beginning of the summer was 4,000. The population of mosquitoes is expected to grow at a rate of 25% a month. How many mosquitoes will there be after 4 months?

• 9765

• 9006

• 5433

• 9766

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 equation that models this graph?

• y = 2(3)^x
• y = 3(2)^x
• y = 3(½)^x
• y =½(3)^x

1. The population of a school of fish decreases at a rate of 18% per month. There are currently 500 fish in the school. How many fish will there be in 24 months?

• 26,555

• 696

• 336

• 4