The half-life of potassium-40 is 1.3 billion years. If a rock that formed 2.6 billion years ago originally contained 5 grams of potassium-40, about __________ grams of potassium-40 would be left in that rock today.
A) 0.0125
B) 0.125
C) 1.25
D) 0.25

Question

Quizplus · Accepted Answer

After 2.6 billion years, which is two half-lives of potassium-40 (1.3 billion years each), the amount of potassium-40 would have halved twice. Starting with 5 grams, after the first half-life, it would be 2.5 grams, and after the second half-life, it would be 1.25 grams.

The Half-Life of Potassium-40 Is 1