Given data
*The amount of gold-198 is N = 100 g
*The amount of gold decays is n = 6.25 g
*The given number of days is T = 10.8 days
The expression for the radioactivity decay is given as
[tex]N=n(0.5)^{\frac{T}{t}}[/tex]*Here t is the half-life period
Substitute the values in the above expression as
[tex]\begin{gathered} 100=6.25(0.5)^{\frac{10.8}{t}} \\ t=2.7\text{ days} \end{gathered}[/tex]