Question: Susan monitors the number of strep infections reported in a certain neighborhood in a given week. The recent numbers are shown in this table:
Week Number of People
0 20
1 26
2 34
3 44
According to her reports, the reported infections are growing at a rate of 30%.
If the number of infections continues to grow exponentially, what will the number of infections be in week 10?
1. **State the problem:** We want to find the number of infections in week 10, given that infections grow exponentially at a rate of 30% per week.
2. **Formula for exponential growth:** The number of infections at week $t$ is given by $$N(t) = N_0 \times (1 + r)^t$$ where:
- $N_0$ is the initial number of infections,
- $r$ is the growth rate (as a decimal),
- $t$ is the number of weeks.
3. **Identify known values:** From the table, at week 0, $N_0 = 20$ infections.
The growth rate is $r = 0.30$ (30%).
4. **Calculate the number of infections at week 10:**
$$N(10) = 20 \times (1 + 0.30)^{10} = 20 \times 1.30^{10}$$
5. **Calculate $1.30^{10}$:**
Using a calculator, $1.30^{10} \approx 13.786$.
6. **Multiply to find $N(10)$:**
$$N(10) = 20 \times 13.786 = 275.72$$
7. **Interpretation:** Since the number of infections must be a whole number, we round to the nearest whole number:
**Final answer:**
$$\boxed{276}$$ infections are expected in week 10 if the exponential growth continues.