#1**+1 **

The way you have your formula written, t is for half-life, which is the exact opposite of doubling time!

Solve for t over the real numbers:

1200/e^(0.025 t) = 600

1200/e^(0.025 t) = 1200 e^(-t/40):

1200/e^(t/40) = 600

Divide both sides by 1200:

e^(-t/40) = 1/2

Take reciprocals of both sides:

e^(t/40) = 2

Take the natural logarithm of both sides:

t/40 = log(2)

Multiply both sides by 40:

**t = 40 log(2) =~ 27.726 Time units.**

Guest Sep 24, 2017