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Finding the time given an exponential function with base [tex]\( e \)[/tex] that models a population.

The number of bacteria [tex]\( P(h) \)[/tex] in a certain population increases according to the following function, where time [tex]\( h \)[/tex] is measured in hours:

[tex]\[ P(h) = 1800 e^{0.18 h} \][/tex]

How many hours will it take for the number of bacteria to reach 2700?

Round your answer to the nearest tenth, and do not round any intermediate computations.

[tex]\[ \boxed{\text{hours}} \][/tex]


Sagot :

To determine how many hours it will take for the number of bacteria to reach 2700 when the population increases according to the function [tex]\( P(h) = 1800 e^{0.18 h} \)[/tex], follow these steps:

1. Understand the given function:

[tex]\( P(h) = 1800 e^{0.18 h} \)[/tex]

where [tex]\( P(h) \)[/tex] represents the population of bacteria at time [tex]\( h \)[/tex] (in hours).

2. Set up the equation:

We need to find [tex]\( h \)[/tex] when [tex]\( P(h) = 2700 \)[/tex]. Substitute 2700 for [tex]\( P(h) \)[/tex]:

[tex]\( 2700 = 1800 e^{0.18 h} \)[/tex]

3. Isolate the exponential term:

Divide both sides of the equation by 1800 to isolate the exponential expression:

[tex]\( \frac{2700}{1800} = e^{0.18 h} \)[/tex]

Simplifying the fraction on the left side:

[tex]\( 1.5 = e^{0.18 h} \)[/tex]

4. Take the natural logarithm of both sides:

Apply the natural logarithm (ln) to both sides to solve for [tex]\( h \)[/tex]:

[tex]\( \ln(1.5) = \ln(e^{0.18 h}) \)[/tex]

Using the property of logarithms [tex]\( \ln(e^x) = x \)[/tex]:

[tex]\( \ln(1.5) = 0.18 h \)[/tex]

5. Solve for [tex]\( h \)[/tex]:

Divide both sides of the equation by 0.18 to isolate [tex]\( h \)[/tex]:

[tex]\( h = \frac{\ln(1.5)}{0.18} \)[/tex]

Calculate [tex]\( \ln(1.5) \)[/tex] first and then perform the division.

Note: Since we are instructed not to round any intermediate computations, consider the precise value obtained here.

6. Result:

The value obtained for [tex]\( h \)[/tex] is approximately [tex]\( 2.252583933934247 \)[/tex].

Rounding this to the nearest tenth:

[tex]\( h \approx 2.3 \)[/tex] hours

Therefore, it will take approximately [tex]\( 2.3 \)[/tex] hours for the number of bacteria to reach 2700.