Question:

Rocks brought back from the Moon were estimated to have 8% of the ⁴⁰K (Potassium) that it initially had. (It turns into ⁴⁰Ar.) How long ago were these rocks formed? This indicates how long it has been

Rocks brought back from the Moon were estimated to have 8% of the ⁴⁰K (Potassium) that it initially had. (It turns into ⁴⁰Ar.) How long ago were these rocks formed? This indicates how long it has been since the Moon was hot and molten.
a. After 10,000 years, what fraction of a sample of 40K is left over?
b. After 1,000 years, what fraction of a sample of 40K is left over?

Rocks brought back from the Moon were estimated to have 8% of the ⁴⁰K (Potassium) that it initially had. (It turns into ⁴⁰Ar.) How long ago were these rocks formed? This indicates how long it has been since the Moon was hot and molten. a. After 10,000 years, what fraction of a sample of 40K is left over? b. After 1,000 years, what fraction of a sample of 40K is left over?