A sample contains 10.5 g of the radioisotope Pb-212 and 157.5 g of its daughter isotope, Bi-212. How many half-lives have passed since the sample originally formed?

4

14

15

147.5

The right answer for the question that is being asked and shown above is that: "15." A sample contains 10.5 g of the radioisotope Pb-212 and 157.5 g of its daughter isotope, Bi-212. There are 15 half-lives that have passed since the sample originally formed