An unknown radioactive element decays into non-radioactive substances. In days the radioactivity of a sample decreases by percent. What is the half life of the element in days?
[IMG]file:///C:/Users/WILS58%7E1.003/AppData/Local/Temp/moz-screenshot.png[/IMG][IMG]file:///C:/Users/WILS58%7E1.003/AppData/Local/Temp/moz-screenshot-1.png[/IMG]How long will it take for a sample of 100 mg to decay down to 60 mg? How many days?