The Choices
Which answer is correct?
The Rule of 72 says money doubles every ~10 years at this rate.
- A $31,000
- B $52,000
- C $76,123
- D $110,000
Answer: C · $76,123
$10,000 at 7% compounded annually for 30 years becomes about $76,123. That is the power of letting time do the heavy lifting.
The money lesson
The answer is $76,123. The Rule of 72 gets you close: money doubles every ~10.3 years at 7%. Three doublings is roughly 8×.
This puzzle is designed to make one financial rule easier to remember. Use it as a starting point, then run your own numbers before making a real-world decision.