After the closing of the mill, the town of Sawyerville experienced a decline in its population.The relationship between the elapsed time, t, in years, since the closing of the mill, and the town's population, P(t), is modeled by the following function.P(t)=12,000⋅2−15tIn how many years will Sawyerville's population be 9000 ? Round your answer, if necessary, to the nearest hundredth.years
Q. After the closing of the mill, the town of Sawyerville experienced a decline in its population.The relationship between the elapsed time, t, in years, since the closing of the mill, and the town's population, P(t), is modeled by the following function.P(t)=12,000⋅2−15tIn how many years will Sawyerville's population be 9000 ? Round your answer, if necessary, to the nearest hundredth.years
Write population function and target: Write down the given population function and the target population.The population function is P(t)=12,000×2−(15t), and we want to find the time t when the population P(t) is 9000.
Solve for : Set the population function equal to and solve for t.\newline900090009000 = 121212,000000000 \times 222^{-\left(\frac{t}{151515}\right)}
Isolate exponential term: Divide both sides of the equation by 12,00012,00012,000 to isolate the exponential term.\newline9,00012,000=2−(t15)\frac{9,000}{12,000} = 2^{-\left(\frac{t}{15}\right)}12,0009,000=2−(15t)
Simplify left side: Simplify the left side of the equation. 900012,000=34\frac{9000}{12,000} = \frac{3}{4}12,0009000=43
Convert fraction to decimal: Convert the fraction to a decimal to make it easier to work with. 34=0.75\frac{3}{4} = 0.7543=0.75
Take natural logarithm: Now we have the equation 0.75=2−(t15)0.75 = 2^{-\left(\frac{t}{15}\right)}0.75=2−(15t). Take the natural logarithm (ln) of both sides to remove the exponent.\newlineln(0.75)=ln(2−(t15))\ln(0.75) = \ln\left(2^{-\left(\frac{t}{15}\right)}\right)ln(0.75)=ln(2−(15t))
Simplify using logarithm property: Use the property of logarithms that ln(ab)=b⋅ln(a)\ln(a^b) = b \cdot \ln(a)ln(ab)=b⋅ln(a) to simplify the right side of the equation.\newlineln(0.75)=−t15⋅ln(2)\ln(0.75) = -\frac{t}{15} \cdot \ln(2)ln(0.75)=−15t⋅ln(2)
Divide by −ln(2)-\ln(2)−ln(2): Divide both sides by −ln(2)-\ln(2)−ln(2) to solve for ttt.t=15⋅ln(0.75)−ln(2)t = \frac{15 \cdot \ln(0.75)}{-\ln(2)}t=−ln(2)15⋅ln(0.75)
Calculate t using calculator: Calculate the value of t using a calculator.\newlinet≈15×ln(0.75)/−ln(2)t \approx 15 \times \ln(0.75) / -\ln(2)t≈15×ln(0.75)/−ln(2)\newlinet≈15×(−0.28768)/−0.693147t \approx 15 \times (-0.28768) / -0.693147t≈15×(−0.28768)/−0.693147\newlinet≈15×0.28768/0.693147t \approx 15 \times 0.28768 / 0.693147t≈15×0.28768/0.693147\newlinet≈4.3452/0.693147t \approx 4.3452 / 0.693147t≈4.3452/0.693147\newlinet≈6.271t \approx 6.271t≈6.271
Round to nearest hundredth: Round the answer to the nearest hundredth. t≈6.27t \approx 6.27t≈6.27 years
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