radioactive Carbon 14 in a dead organism decays according to the equation A=A e^.000124t where t is in years and A0 is the amount at t=0. Estimate the age of a skull uncovered in an archeological site if 10% of the original Carbon 14 is still present.

Answer 1

A = Ao*e(^0.000124t)

If the final amount, A, is equal to 10% of initial amount, Ao, thus
0.1*Ao = Ao*e(^0.000124t)
0.1 = e(^0.000124t)

Get the ln of both sides:
ln (0.1) = ln(e(^0.000124t))
ln (0.1) = 0.000124t

Now solve for t. Just one clarification, I think the exponent of e should be negative if it's a decay problem. Because if not, the time that would be solved would be negative, and time cannot be negative.
Hope this helps~ `u`