Answer:
(a)140 years
(b)20 years
(c)8.75 years
Explanation:
The Rule of 70 is used in accounting to estimate the duration(number of years) it will take for the initial investment (P) to double in value given a particular interest rate (r) and an annual compounding period.
The Formula for the Rule of 70 is:
[tex]\text{Number of Years to Double}=\frac{70}{\text{Annual Rate of Return}}[/tex]
(a)Savings account earning 0.50% interest
[tex]\text{Number of Years to Double}=\frac{70}{0.5}=140 years[/tex]
(b)A U.S. Treasury bond earning 3.50% interest
[tex]\text{Number of Years to Double}=\frac{70}{3.5}=20 years[/tex]
(c)A stock market mutual fund earning 8.00% interest
[tex]\text{Number of Years to Double}=\frac{70}{8}=8.75 years[/tex]