Pre calculus

Question

any principal amount invest at 5% annual interest takes 15 years to double. How many years does it take for the principal amount to triple?

Answer 1

If P = principal amount, use compound interest formula and get:

3P = P * (1 + .05)^t
With t = the amount of time it to triple

Divide both sides by P and get

3 = (1.05)^t
Use natural log on both sides and use the exponential log rule to get:

ln 3 = t * ln 1.05

Solve for t and ROUND UP to the nearest year, and that will be your answer.