Atoms of X decay to atoms of Y with a half-life of 500,000 y. If there were 50,000 atoms of X present at the start and 0 atoms of Y, how long will it take for there to be 3,125 atoms of X?
A fossil that formed with 10,000 atoms of a radioactive parent element now contains only 1,250 atoms of that element. If the half-life of the element was 1,000,000 y, how old is the fossil?
The age of a rock was was estimated using 238U radiometric dating. The ratio of 238U to 206Pb (238U decays to 206Pb) was approximately equal to 1. If the half-life of 238U is 4.5 billion y, and if it is assumed there was no 206Pb initially, how old is the rock sample?