Suppose that radio active material is given by the equation A(t)=119e-0.25t, What is the half-life? (Round your answer to 4 decimal places.)

Answer 1

A(t) = 119e^-.25t

what is the half life?

119/2 = 119e^-.25t

1/2 = e^-.25t (the 119 is irrelevant. You could have started with any initial amount, and the half life would be no different)

take natural logs of both sides to get

ln(.5) = -.25t

divide by -.25

t = ln(.5)/-.25 = about 2.7726 years half life

use a calculator with a natural log function