Answer :
Given data
*The initial quantity of potassium-42 is 1500 mg
*The given time is t = 48 hours
*The half-life of Potassium - 42 is T = 12.4 hours
The expression for the radioactive decay is given as
[tex]A(t)=A_0(\frac{1}{2})^{\frac{t}{T_{}_{}_{}}}[/tex]Substitute the values in the above expression as
[tex]\begin{gathered} A(48)=1500(\frac{1}{2})^{\frac{48}{12.4}} \\ =102.59\text{ mg} \end{gathered}[/tex]