Question

Situation:
A 15 gram sample of a substance that's a by-product of fireworks has a k-value of .1405.
find the substance's half-life, in days. round to the nearest tenth

Answer 1

I answered your other question

Answer 2

\[f(t) = A*e^{-kt}\]
if f(t)/A = .5:
\[.5 = e^{-kt}; -kt = \ln (.5); t = \ln(.5)/-k = 4.9 days\]

Answer 3

4.9 is the answer