RatedrillRate needed to double
A time value of money problem from Ratedrill. Solve it with one answer box, with fresh numbers on every attempt and the formula, calculator keystrokes and Excel version in the worked answer, and it is checked the moment you submit.
The task
You want an investment to double in exactly 4 years with annual compounding and no further deposits. What annual rate of return do you need? Give the exact rate, not a rule of thumb.
What this problem teaches
The Rule of 72 estimate is 72 / 4 = 18%: close, but not exact.
A hint if you get stuck
Doubling means FV / PV = 2, so (1 + r)^n = 2 and r = 2^(1/n) - 1.
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The first 15 tasks on Ratedrill are free. Open it on the practice page, solve it, and get instant feedback with a hint. A free account adds the worked solution; Pro adds timed mode and the certificate.
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