Simplify the following text for a Grade 11 native English-speaking person.
Original: Radiometric dating ( often called radioactive dating ) is a technique used to date materials such as rocks , usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products , using known decay rates .
Simplified: Radiometric dating ( often called radioactive dating ) is a technique used to date materials . The method compares the amount of a naturally occurring radioactive isotope and its decay products , in samples .