USING EXPONENTIAL AND LOGARITHMIC FUNCTIONS

fumerios:

Modern whales appeared 5-10 million years ago. The vertebrae of a whale discovered by paleontologists contain roughly 0.25% as much carbon-14 as they would have contained when the whale was alive. How long ago did the whale die? Use k = 0.00012.

Umm
Isn't that A=A ₀ * e ^-kt

0.0025=1 * e ^-0.00012t

ln(0.0025)= ln e ^-0.00012t

ln(0.0025)= -0.00012t * ln e

ln(0.0025)= -0.00012t

t = -ln(0.0025) / 0.00012

49,929 years ago ( assuming that the time frame is in years)

I think that's right but I am not positive.