1. **Stating the problem:** We are given population data over time and need to find an equation modeling this growth.
2. **Observing the data:** The population increases from 35.0 to 75.6 thousand over 10 years, suggesting exponential growth.
3. **Exponential growth model:** The general form is $$P(t) = P_0 \cdot d^t$$ where:
- $P(t)$ is the population at time $t$,
- $P_0$ is the initial population,
- $d$ is the growth factor per year,
- $t$ is the time in years since 1996.
4. **Identify initial population:** At $t=0$, $P(0) = 35.0$ thousand, so $P_0 = 35.0$.
5. **Find growth factor $d$:** Use a known point, for example at $t=1$, $P(1) = 37.8$.
6. **Set up equation:** $$37.8 = 35.0 \cdot d^1$$
7. **Solve for $d$:**
$$d = \frac{37.8}{35.0} = 1.08$$
8. **Check with another point:** At $t=10$, $P(10) = 75.6$.
Calculate predicted population:
$$P(10) = 35.0 \cdot (1.08)^{10}$$
Calculate $(1.08)^{10}$:
$$1.08^{10} \approx 2.1589$$
So,
$$P(10) \approx 35.0 \times 2.1589 = 75.56$$ which matches the data closely.
9. **Final model:**
$$\boxed{P(t) = 35.0 \cdot (1.08)^t}$$
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**Why is $d$ not zero in exponential functions?**
- The growth factor $d$ represents how much the population multiplies each year.
- If $d$ were zero, the population would be zero for all $t > 0$, which contradicts the data.
- Since the population grows, $d$ must be greater than zero and typically greater than 1 for growth.
Hence, $d$ is approximately 1.08, not zero.
Population Growth 03777E
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