<PRE><B>Question 1038087</B>
Can do the first two here.
A=Ao(1+.07/12)^12t
A=2 Ao
2=(1+.0058333)^12t
ln of both sides
ln2=12t*ln (1.00583333)
without rounding, divide both sides by ln(1.0583333)
then divide both by 12
t=9.93 years
The rule of 72 would say about 10 years.  This is reasonable.
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15000=200(1+(.0725)/4)^4t
75=[1+(.0725)/4)]^4t
ln 75=4t ln (1+(0.0725)/4))
t=60.09 years

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