A sample of radioactive material decays over time (measured in hours) with decay constant .2. The graph of the exponential function y = P(t) in Fig. 7 gives the number of grams remaining after t hours.

(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?

9 7 5 3 1 y 1 Figure 7 y = P(1) 3 5 7 9