How many years would it take for an investment of 280000 to

How many years would it take for an investment of $280,000 to accumulate to at least $425,000 at 15% per year interest?

Let the required number of years = N.

Then,

Future value (FV) = Present value (PV) x (1 + r)^N

(1 + r)^N = FV / PV

(1.15)^N = $425,000 / $280,000 = 1.5179

Taking logarithms each side,

N x ln 1.15 = ln 1.5179

N x 0.1398 = 0.4193

N = 0.4193 / 0.1398 = 3 years