18.5 is correct for part (a) since t = 0 leads to A = 18.5
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Part (b)
Your teacher is asking for the value of t when A = 26.6
A = 18.5*e^(0.1708t)
26.6 = 18.5*e^(0.1708t)
26.6/18.5 = e^(0.1708t)
1.437838 = e^(0.1708t)
Ln(1.437838) = 0.1708t
t = Ln(1.437838)/0.1708
t = 2.126116 approximately
t = 2 when rounding down to the nearest integer
Therefore, 2 years after the year 2000, the year 2002, is when the population reaches roughly 26.6 million. The actual population will be slightly less than 26.6 million, but it's close enough.
Note that:
- 18.5*e^(0.1708*2) = 26.033 approximately
- 18.5*e^(0.1708*3) = 30.882 approximately
which helps confirm the correct value of t is between t = 2 and t = 3.
Answer: 2002