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The area of undeveloped land in a suburban town is decreasing at a rate of [tex]$17.3 \%$[/tex] annually. In 2016, there were 3,400 acres of undeveloped land. If [tex]$t$[/tex] represents the number of years since 2016, which equation can be used to determine after how many years the town will have 900 acres of undeveloped land remaining?

A. [tex]$900=3,400(1.173)^t$[/tex]

B. [tex]$3,400=900(0.173)^t$[/tex]

C. [tex]$900=3,400(0.827)^t$[/tex]

D. [tex]$3,400=900(0.9827)^t$[/tex]


Sagot :

Let's solve the problem step-by-step to find the correct equation that represents the scenario given:

1. Understand the problem:
- We have an initial amount of undeveloped land: 3,400 acres in 2016.
- The land is decreasing at a rate of 17.3% per year.
- We need to find an equation that tells us after how many years the remaining undeveloped land will be 900 acres.

2. Identify the components of an exponential decay equation:
- The general form of an exponential decay equation is [tex]\( A = A_0(1 - r)^t \)[/tex], where:
- [tex]\( A \)[/tex] is the amount remaining after time [tex]\( t \)[/tex],
- [tex]\( A_0 \)[/tex] is the initial amount,
- [tex]\( r \)[/tex] is the decay rate (expressed as a decimal),
- [tex]\( t \)[/tex] is the time in years.

3. Substitute the given values:
- Initial amount, [tex]\( A_0 \)[/tex]: 3,400 acres.
- Remaining amount, [tex]\( A \)[/tex]: 900 acres.
- Decay rate, [tex]\( r \)[/tex]: 17.3% or 0.173.

4. Form the equation:
- Based on the exponential decay formula, we have:
[tex]\[ 900 = 3400(1 - 0.173)^t \][/tex]
- Simplifying inside the parentheses:
[tex]\[ 1 - 0.173 = 0.827 \][/tex]
- Thus, the equation becomes:
[tex]\[ 900 = 3400(0.827)^t \][/tex]

5. Match with the provided options:
- Option A: [tex]\( 900 = 3,400(1.173)^t \)[/tex]
- Option B: [tex]\( 3,400 = 900 (0.173)^t \)[/tex]
- Option C: [tex]\( 900 = 3,400(0.827)^t \)[/tex]
- Option D: [tex]\( 3,400 = 900(0.9827)^t \)[/tex]

After comparing our derived equation with the options provided, we see that the correct equation is given by:

[tex]\[ \boxed{900 = 3400(0.827)^t} \][/tex]

Thus, the correct answer is:
[tex]\[ C. \; 900 = 3,400(0.827)^t \][/tex]