Question

You are trying to determine the half-life of a new radioactive element you have isolated. You start with 1 gram, and 4 days later you determine that it has decayed down to 0.6 grams. What is its half-life? (Round your answer to three significant digits.)

Answer 1

Start with general exponential decay function:
P = e^{-kt}

Plug in given point (4,0.6) solve for k
k = ln 0.6/-4 to determine half-life,

set P = 0.5 , solve for t

t = 4* \\ 0.5/ln 0.6