Answer:
Step-by-step explanation:
3/10 + infinite number of fractions.
30%
0.3
If y(t) is the mass (in mg) remaining after t years, then y(t) = y(0) (0.5)^{t/T} = 400 (0.5)^{t /4}, where T is the half-life period and y(0) is the amount at t = 0 years (initial).
Then at t = 20:
y(20) = 400 (0.5)^{20 /4} = \text{12.5 mg}
23 and 40
9
