A 5,560 Ci 60 Co source used for cancer therapy is considered too weak to be useful when its activity falls to 3,500 Ci. How long (in years) after its manufacture does this happen?

A 228Th source is labeled 1.50 mCi, but its present activity is found to be 1.73 ✕ 106 Bq. A.)  What is the present activity in mCi? =______mCi B.) How long ago did it actually have a 1.50-mCi activity? =_____y

A piece of radium has an activity of 92 mCi. (b) What is its activity in Bq?

14 A sample has a ¹4C activity of 0.0027 Bq per gram of carbon. (a) Find the age of the sample, assuming that the activity per gram of carbon in a living organism has been constant at a value of 0.23 Bq. (b) Evidence suggests that the value of 0.23 Bq might have been as much as 27% larger. Repeat part (a), taking into account this 27% increase. (a) Number i (b) Number i Units Units