The half life of radon-222 is 3.8 days. How much of a 100 gram sample is left after 15.2 days?

6.25 g of radon-222 is left over after 15.2 days

Explanation:

You must start by finding out how many half lives have occurred over the time. This can be done by dividing the time passed by the half-life.

15.2/3.8=4

Now that the amount of half-lives is known now you must take that amount away from the original sample.

100/2=50

50/2=25

25/2=12.5

12.5/2=6.25

the fossil record provides evidence of a common ancestor to many species.