Answer:
A. $96.00, $38.40, $15.36
B. after 6 years
Step-by-step explanation:
An exponential function has the general form ...
y = (initial value) × (growth factor)^t
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<h3>A.</h3>
The growth <em>factor</em> is 1 more than the growth <em>rate</em>. Here, the "growth" is actually a decay at the rate of 60% per year, so the growth rate is -0.60. The initial value is $240. The value equation can be written ...
y = 240(1 -0.60)^t
We want the value after t=1, t=2, and t=3 years.
y = $240(0.4)^1 = $96 . . . value after 1 year
y = $240(0.4)^2 = $38.40 . . . value after 2 years
y = $240(0.4)^3 = $15.36 . . . value after 3 years
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<h3>B.</h3>
We want to find t when y < 1.
240(0.4)^t < 1
0.4^t < 1/240 . . . . . . . . . . . . divide by 240
t × log(0.4) < log(1/240) . . . take logs
t > log(1/240)/log(0.4) . . . . . . . inequality reverses because log(0.4) < 0
t > 5.98
The bike will be worth less than $1 after about 6 years.
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<em>Additional comment</em>
For part A, we have shown the values after 1, 2, and 3 years. The expressions are shown on the same line preceding the value.
