Chapter 5.1, Problem 45E

Radioactive Decay A sample of radioactive material decays over time (measured in hours) with decay constant $.2$. The graph of the exponential function $y=P\left(t\right)$ in Fig.7 gives the number of grams remaining after $t$ hour [Hint: In parts (c) and (d) use the differential equation satisfied by $P\left(t\right)$.]

a. How much was remaining after $1$ hour?

b. Approximate the half-life of the material.

c. How fast was the sample decaying after $6$ hours?

d. When was the sample decaying at the rate of $. 4$ grams per hour?