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In 2010, the population of a city was 242,000. From 2010 to 2015, the population grew by 5.9%. From 2015 to 2020, it fell by 4.8%. To the nearest 100 people, what was the population in 2020?

1 Answer

11 votes

Answer:

244000

Explanation:

The growth is a 5.9% increase, the fall is a 4.8% decrease

\color{green}{5.9\%\text{ increase}}=

5.9% increase=

\,\,100\%+5.9\%=\color{green}{105.9\%}

100%+5.9%=105.9%

\color{red}{4.8\%\text{ decrease}}=

4.8% decrease=

\,\,100\%-4.8\%=\color{red}{95.2\%}

100%−4.8%=95.2%

\color{darkviolet}{\text{2020 pop}}=

2020 pop=

\,\,\color{red}{95.2\%}\text{ of }\color{green}{105.9\%}\text{ of }\color{blue}{\text{2010 pop}}

95.2% of 105.9% of 2010 pop

=

=

\,\,\color{red}{0.952}\times\color{green}{1.059}\times\color{blue}{242000}

0.952×1.059×242000

95.2% = 0.952

105.9% = 1.059

=

=

\,\,\color{darkviolet}{243976.656}

243976.656

\approx

\,\,\color{darkviolet}{244000}

244000

Round to the nearest 100 people

\text{The population in 2020 was 244000 people.}

The population in 2020 was 244000 people.

Method 2

\color{green}{\text{growth}}=

growth=

\,\,\text{5.9\% of \color{blue}{\text{2010 population}}}

5.9% of 2010 population

=

=

\,\,0.059\times\color{blue}{242000}

0.059×242000

5.9% = 0.059

=

=

\,\,\color{green}{14278}

14278

\color{darkorange}{\text{2015 population}}=

2015 population=

\,\,\color{blue}{\text{2010 population}}+\color{green}{\text{growth}}

2010 population+growth

=

=

\,\,\color{blue}{242000}+\color{green}{14278}

242000+14278

=

=

\,\,\color{darkorange}{256278}

256278

\color{red}{\text{decrease}}=

decrease=

\,\,4.8\%\text{ of }\color{darkorange}{\text{2015 population}}

4.8% of 2015 population

=

=

\,\,0.048\times\color{darkorange}{256278}

0.048×256278

4.8% = 0.048

=

=

\,\,\color{red}{12301.344}

12301.344

\color{darkviolet}{\text{2020 population}}=

2020 population=

\,\,\color{darkorange}{\text{2015 population}}-\color{red}{\text{decrease}}

2015 population−decrease

=

=

\,\,\color{darkorange}{256278}-\color{red}{12301.344}

256278−12301.344

=

=

\,\,\color{darkviolet}{243976.656}

243976.656

\approx

\,\,\color{darkviolet}{244000}

244000

Round to the nearest 100 people

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