The continuous compound interest formula is:

Where:

- P = Principal amount (initial investment)
- r = Annual interest rate (as a decimal)
- t = Number of years
- A = Amount after time t
- e = Exponential function

From the question, we can deduce that P=$10,000, r=0.06, t=?, A=$25,000 and hence inserting the values into the formula gives:

Now, solve for and you will have the amount of years for the investment to grow from $10000 to $25000 with continuous compound interest.