• Feb 9th 2010, 04:25 PM
tactical
I have the following equation.

$\displaystyle N/6= N*exp(-.0001216t)$

Then I want to solve to t, and the solution is $\displaystyle ln(6)/.00001216$

I must be missing something....why is $\displaystyle ln(6)$ and not $\displaystyle ln(1/6)$?
• Feb 9th 2010, 04:30 PM
dedust
Quote:

Originally Posted by tactical
I have the following equation.

$\displaystyle N/6= N*exp(-.0001216t)$

Then I want to solve to t, and the solution is $\displaystyle ln(6)/.00001216$

I must be missing something....why is $\displaystyle ln(6)$ and not $\displaystyle ln(1/6)$?

$\displaystyle N/6= N*exp(-.0001216t)$

$\displaystyle 1/6= exp(-.0001216t)$

$\displaystyle 6= exp(0.0001216t)$

$\displaystyle \ln 6= (0.0001216t)$

$\displaystyle t = \frac{\ln 6}{0.0001216}$
• Feb 10th 2010, 02:12 AM
HallsofIvy
Quote:

Originally Posted by tactical
I have the following equation.

$\displaystyle N/6= N*exp(-.0001216t)$

Then I want to solve to t, and the solution is $\displaystyle ln(6)/.00001216$

I must be missing something....why is $\displaystyle ln(6)$ and not $\displaystyle ln(1/6)$?

You could also write the answer as t= ln(1/6)/(-.0001216). Now ln(1/6)= -ln(6).