Edward C. answered • 03/30/15

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The formula for compound interest is A = Pe

^{rt}whereA = Accumulated or final amount

P = Principal or original amount

r = Rate as a decimal

t = time

The investment will double when A = 2*P so solve

2*P = Pe

^{0.065t}e

^{0.065t}= 2Take the natural log of both sides

0.065t = ln(2)

t ln(2)/0.065 ~ 10.7 years