Question: You are analyzing rocks that contain small amounts of potassium-40 and argon-40. The half-life of potassium-40 is 1.25 billion years. Assume that when the rocks initially formed they did not contain any argon-40.
(a) You find a rock that contains equal amounts of potassium-40 and argon-40. How old is it? Explain.
(b) You find a rock that contains three times as much argon-40 as potassium-40. How old is it? Explain.