Answer:
1.25kg
Step-by-step explanation:
useing the problem the half life equation will be:
f(x)=5(0.5)^(x/140)
x is amount of days
so plugging in 280 for x will get 1.25kg
1/1/2 is the answer ............
I think it would be D, because you would divide the 1/8 be 5, giving you 1/40
