The half-life of radium is 1600 years. What is the fraction of sample undecayed after 6400 years? The half-life of radium is 1600 years. What is the fraction of sample undecayed after 6400 years? November 28, 2020 Category: AIIMS Last 24 Years Solved 1996 - 2019 Physics and Chemistry Video Solutions , Chapter 31 - [...]