OpenStudy (anonymous):

The following table shows the currently accepted half-life values for six parent isotopes. Uranium-238 4.5 billion years Uranium-235 704 million years Thorium-232 14.0 billion years Rubidium-87 48.8 billion years Potassium-40 1.25 billion years Samarium-147 106 billion years Earth is approximately 4.5 billion years old. Given this information and the data in the table, which of the following isotopes could today contain less than 50 percent of its parent isotope?

OpenStudy (anonymous):

The multiple choices are A. Potassium-40 B. Rubidium-87 C. Samarium-147 D. Uranium-238

OpenStudy (frostbite):

Try make a guess and explain why this time. Use the same argument I used in the last one.

OpenStudy (frostbite):

Can help make some rules that are easy to remember: Half life = Time (Earth's life team) -> Percentage = 50% Half life < Time (Earth's life team) -> Percentage < 50% Half life > Time (Earth's life team) -> Percentage > 50%

OpenStudy (anonymous):

It would be Potassium-40 due to its half-life value being less than the Earth's age.

OpenStudy (anonymous):

Am I correct?

OpenStudy (anonymous):

Are you still there? I am confused no what to do or how to start this.

OpenStudy (anonymous):

*on I apologize for my misspelling.

OpenStudy (anonymous):

Never mind, it seems Potassium-40 was indeed the answer. Thank you again for all your help!

OpenStudy (frostbite):

Sorry I fell asleep. But it looks like you can do it :) You are not totally lost.