Question

half life of a drug in the bloodstream is 14 hours. By what factor does the concentration of the drug decrease in 22 hours?

Answer 1

The model is an exponential function such that
e^rt=(1/2)
where t=14 hours.

e^(14r)=1/2
14r=ln(1/2)
r=ln(1/2) / 14
=-.04951 (approx).

In 22 hours,
factor=e^(-0.04951*22)
=0.336475 approx.