Using the rule of 70, about how much would $100 be worth after 50 years if the interest rate were 7 percent?

The rule of 70 states that the doubling time or the time required to double an investment is equivalent to 70 divided by the interest rate. So in this case the interest rate is 7%, so the doubling period is:

doubling period = 70 / 7 = 10 years

Therefore the investment doubles every 10 years. So:

0 year = $100

10 year = $200

20 year = $400

30 year = $800

40 year = $1600

50 year = $3200

Answer:

$3200