Question 979641
3000=150{1+(0.025/12)}^12t ; t=years.  divide the interest by the number of compoundings per year and raise it to the number of years * 12 months/year.

As a note, this has to double more than 4 times, and the rule of 72 for doubling, which can loosely be used for this, suggests that doubling will take 29 years.  This will take somewhere in the neighborhood of 120-140 years.

20={1+0.002083}^12t
ln of both sides
ln 20= 12t ln (1.002083)
2.9957=12 t *(0.002080)
without rounding yet
do ln20/(12*0.002080) =t

t=119.973 years.