High School

Initially, there were 197 weeds in a park. The weeds grew at a rate of [tex]25 \%[/tex] each week. The following function represents the weekly weed growth: [tex]f(x) = 197(1.25)^x[/tex].

Rewrite the function to show how quickly the weeds grow each day and calculate this rate as a percentage:

A. [tex]f(x) = 197(1.25)^{7x}[/tex]: grows at a rate of approximately [tex]2.5 \%[/tex] daily

B. [tex]f(x) = 197\left(1.25^7\right)^x[/tex]: grows at a rate of approximately [tex]4.77 \%[/tex] daily

C. [tex]f(x) = 197(1.03)^x[/tex]: grows at a rate of approximately [tex]0.3 \%[/tex] daily

D. [tex]f(x) = 197(1.03)^{7x}[/tex]: grows at a rate of approximately [tex]3 \%[/tex] daily

Answer :

To determine the daily growth rate of weeds, we need to start with the given weekly growth rate function:

[tex]\[ f(x) = 197(1.25)^x \][/tex]

This function shows that the weeds grow by 25% per week. We want to find the equivalent daily growth function and express this rate as a percentage.

Step 1: Relate the Weekly and Daily Growth Rates

The weekly growth rate is given as a factor of 1.25. We use the fact that a week has 7 days. So, we need to find a daily growth rate [tex]\( r \)[/tex] such that:

[tex]\[ (1 + r)^7 = 1.25 \][/tex]

Step 2: Solve for the Daily Growth Rate

We can solve for [tex]\( r \)[/tex] by taking the 7th root of 1.25:

[tex]\[ 1 + r = \sqrt[7]{1.25} \][/tex]

The value of [tex]\( \sqrt[7]{1.25} \)[/tex] gives us the daily growth factor. After determining this factor, subtract 1 to get the daily growth rate [tex]\( r \)[/tex]:

[tex]\[ r = \sqrt[7]{1.25} - 1 \][/tex]

Step 3: Convert the Daily Growth Rate into a Percentage

To express the daily growth rate as a percentage, we multiply it by 100:

[tex]\[ \text{Daily Growth Rate (\%)} = (r) \times 100 \][/tex]

Final Step: Interpret the Result

Carrying out the steps above, we find that the daily growth rate as a percentage is approximately 3.24%. Therefore, the daily growth function can be written as:

[tex]\[ f(x) = 197(1.032391184710001797)^x \][/tex]

This growth rate matches approximately with one of the choices given in the question, indicating it grows at a rate of approximately [tex]\( 3.24\% \)[/tex] daily.