A new car is purchased for 18600 dollars. The value of the car depreciates at 14% per year. To the nearest tenth of a year, how long will it be until the value of the car is 6800 dollars?Answer:
Q. A new car is purchased for 18600 dollars. The value of the car depreciates at 14% per year. To the nearest tenth of a year, how long will it be until the value of the car is 6800 dollars?Answer:
Identify type of depreciation: Determine the type of depreciation.The car depreciates at a constant percentage each year.This is an example of exponential decay.
Find initial value, rate, final value: Identify the initial value a, the rate of depreciation r, and the final value P(t).Initial value a = $18,600Rate of depreciation r = 14% per year or 0.14 as a decimalFinal value P(t) = $6,800
Set up exponential decay formula: Set up the exponential decay formula.The formula for exponential decay is P(t)=a⋅(1−r)t, where P(t) is the value after time t, a is the initial value, and r is the rate of decay.
Plug in known values: Plug in the known values into the exponential decay formula.6800=18600×(1−0.14)t
Solve for t: Solve for t.First, divide both sides by $18,600 to isolate the exponential part of the equation.$6,800/$18,600=(1−0.14)t0.3655913978494624=0.86t
Take natural logarithm: Take the natural logarithm of both sides to solve for t.ln(0.3655913978494624)=ln(0.86t)
Use logarithm property: Use the property of logarithms that ln(ab)=b⋅ln(a).ln(0.3655913978494624)=t⋅ln(0.86)
Divide by ln(0.86): Divide both sides by ln(0.86) to solve for t.t=ln(0.86)ln(0.3655913978494624)
Calculate value of t: Calculate the value of t using a calculator.t≈ln(0.86)ln(0.3655913978494624)t≈7.267
Round to nearest tenth: Round the answer to the nearest tenth of a year.t≈7.3 years
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