A city has a population of 50,000 in 2012. If the population of the city grows at an annual rate of 2%, the year in which the population will reach 100,000 is _____________ and the year it will reach 200,000 is _____________. Show work:

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Answer:

The population will reach 100,000 in 2047.

The population will reach 200,000 in 2082.

Step-by-step explanation:

The compounded growth formula:

[tex]A=P(1+r)^t[/tex]

A= Population after t years

P= Initial amount of population

r= rate of growth

t= Time in years

Given that,

P=50,000, r=2% =0.02, A=100,000

[tex]\therefore 100,000=50,000(1+0.02)^t[/tex]

[tex]\Rightarrow 1.02^t=\frac{100,000}{50,000}[/tex]

[tex]\Rightarrow 1.02^t=2[/tex]

Taking ln both sides

[tex]\Rightarrow ln(1.02^t)=ln|2|[/tex]

[tex]\Rightarrow t\ ln(1.02)=ln|2|[/tex]

[tex]\Rightarrow t=\frac{ln|2|}{ ln(1.02)}[/tex]

[tex]\Rightarrow t\approx 35[/tex]

The population will reach 100,000 in (2012+35)=2047

P=50,000, r=2% =0.02, A=200,000

[tex]\therefore 200,000=50,000(1+0.02)^t[/tex]

[tex]\Rightarrow 1.02^t=\frac{200,000}{50,000}[/tex]

[tex]\Rightarrow 1.02^t=4[/tex]

Taking ln both sides

[tex]\Rightarrow ln(1.02^t)=ln|4|[/tex]

[tex]\Rightarrow t\ ln(1.02)=ln|4|[/tex]

[tex]\Rightarrow t=\frac{ln|4|}{ ln(1.02)}[/tex]

[tex]\Rightarrow t\approx 70[/tex]

The year it will reach 200,000 is (2012+70)=2082