To solve this problem, we can use the Rule of 72, which is a simple way to estimate the number of years required to double the invested money at a fixed annual rate of interest. The formula is:
[tex]\[ \text{Interest Rate} = \frac{72}{\text{Number of Years}} \][/tex]
Here are the steps we'll follow to find the interest rate that will cause Helena's money to double in approximately 38 years:
1. Identify the number of years Helena is willing to wait for her money to double, which is given as 38 years.
2. Apply the Rule of 72 by dividing 72 by the number of years (38) to find the interest rate.
[tex]\[ \text{Interest Rate} = \frac{72}{38} \][/tex]
3. Calculate the result.
After performing the calculation, we get:
[tex]\[ \frac{72}{38} \approx 1.895 \][/tex]
Therefore, the interest rate that will cause Helena's money to double in approximately 38 years is approximately 1.9%.
Looking at the provided choices:
A. 0.5%
B. 1.9%
C. 0.4%
D. 2.3%
The correct answer is:
B. 1.9%
