• Cancers are often treated with radiation.
Radiation kills cells, all cells. When a
person is treated this way, doctors use a
radioactive material which will break down
quickly. Radioactive iodine is one of the
materials used because it has a half-life of
only 8 days.


1. If the doctor places a 12 unit treatment into a tumor, how much of the iodine will remain
after 24 days?

2. How long until only 0.375 units remain?