College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 48

A freshly prepared sample of a certain radioactive isotope has an activity of 10.0 mCi. After 4.00 h, the activity is 8.00 mCi. (a) Find the decay constant and half-life of the isotope. (b) How many atoms of the isotope were contained in the freshly prepared sample (c) What is the sample's activity 30 h after it is prepared