Answer:
1 gram
Explanation:
The equation for half-life given a starting mass, half-life, and amount of days, we can plug it into the half-life equation [tex]R=P(\frac{1}{2})^{\frac{t}{h}[/tex], where R is the remaining amount, P is the starting amount, t is the time, and h is the half-life time of the substance. Plugging in our given values, we get:
[tex]R = 8(\frac{1}{2})^{\frac{42}{14} }=1g[/tex]
There will be 1 gram remaining after 42 days
(Note how this works: 42 days divided by 14 days equals 3 exactly, meaning the initial 8 grams of Phosphorus-32 decays half exactly 3 times during these days, and 8 divided by 2 three times is 1, which is where 1 gram comes from. The fact that this is Phosphorus-32 does not matter, so long as we are already given the half-life already)