Question 1169798
9334=334+(1+(r/12))^228

27.946=(1+(r/12))^228
don't round
ln both sides
3.330=228 ln(1+(r/12))
0.01460=ln(1+(r/12))
raise to e power
1.0147=1+(r/12)
0.0147=r/12
r=17.656%
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this is doubling more than 4 times, and rule of 72 suggests 4 year doubling time, so this doubles four times and almost a 5th
334*2^4=5344, and one more doubling would be over 9334.

alternatively, ln 27=3.33, so in 19 years needs an interest rate of 333/19 in percent, and that is 17.53%, so answer is reasonable.