Question

You deposit $2500 at 4% interest. How long will it take to earn $3000?

Answer 1

assuming compound interest

2500(1.04)^n = 3000
1.04^n = 1.2
use logs

n = log 1.2/log 1.04
= ...

Answer 2

3000=2500(1.04)^t assuming annual interest compounded.

Take log of each side
log3000=log2500 + t log (1.04)
solve for t.