Answer:
Step-by-step explanation:
The formula for this is
[tex]N=N_0(.5)^{\frac{t}{H}[/tex] where
N is the amount of the element left after a certain amount of time (for us it is measured in days),
N₀ is the initial amount of the element in grams,
t is the number of days gone by, and
H is the half life of the element. Filling in:
[tex]N=42(.5)^{\frac{16}{8}[/tex] which simplifies a bit to
[tex]N=42(.5)^2[/tex] and a bit more to
N = 42(.25) which gives us a remaining amount of
N = 10.5
