Answer
(2.) In 5.4 days, 2 half-lives are elapsed.
Work Step by Step
1. Use the half life value for $Au-198$ as a conversion factor to calculate the amount of half-lives after 5.4 days.
number of half lives = $5.4 days \times\frac{1 half-life}{2.7 days} = 2$ half-lives.
