Question 47 of 480
If the population of a town was 240,000 in January 1998 and it increased by 2% each year, what would be the population of the town in January, 2000?
- A. 480,000
- B. 249,696
- C. 249,600
- D. 244,800
Correct Answer:
B
Explanation
To find the population of the town in January 2000, given that it was 240,000 in January 1998 and increased by 2% each year, we can use the formula for compound interest, which is also applicable for population growth. The formula is:
\[
P = P_0 (1 + r)^t
\]
Where:
- \( P \) is the future population.
- \( P_0 \) is the initial population.
- \( r \) is the growth rate (as a decimal).
- \( t \) is the number of years.
### Step-by-Step Calculation
1. **Identify the Variables**:
- Initial population, \( P_0 = 240,000 \)
- Growth rate, \( r = 2\% = 0.02 \)
- Time period, \( t = 2 \) years (from January 1998 to January 2000)
2. **Plug the Values into the Formula**:
\[
P = 240,000 \times (1 + 0.02)^2
\]
3. **Calculate \( (1 + 0.02) \)**:
\[
1 + 0.02 = 1.02
\]
4. **Raise \( 1.02 \) to the power of 2**:
\[
(1.02)^2 = 1.02 \times 1.02 = 1.0404
\]
5. **Multiply by the Initial Population**:
\[
P = 240,000 \times 1.0404
\]
\[
P = 249,696
\]
Thus, the population of the town in January 2000 is **249,696**.
### Explanation of the Correct Option
The correct answer is **B. 249,696**. This is derived from applying the compound growth formula correctly, taking into account the annual growth rate and the number of years.
### Explanation of Why Other Options Are Incorrect
- **A. 480,000**: This option suggests that the population doubled, which would only happen with a 100% increase, not a 2% increase over two years.
- **C. 249,600**: This option is close but incorrect. It seems to be a miscalculation, possibly from incorrectly applying the growth rate or rounding prematurely.
- **D. 244,800**: This option is also incorrect. It may result from misunderstanding the growth calculation or using a wrong formula.
### Common Pitfalls
- **Rounding too early**: Always perform calculations with full precision before rounding the final answer.
- **Misunderstanding the growth rate**: Remember that a 2% increase means multiplying by 1.02, not adding 2% directly to the population.
- **Forgetting to apply the formula correctly**: Ensure you understand the components of the formula and how they relate to the problem.
### Revision Summary
- Use the compound growth formula \( P = P_0 (1 + r)^t \) for population growth.
- Convert percentage growth rates to decimals (e.g., 2% = 0.02).
- Calculate the growth factor for the number of years and multiply by the initial population.
- Be cautious of rounding and ensure calculations are done accurately before arriving at the final answer.