A radioactive substance decays to half its original mass every 15 days. The function gives the approximate mass of the substance, in grams, that remains days after a sample starts to decay. Which statement is the best interpretation of in this context?
The initial mass of the substance was 500 grams.
After 500 days, the mass of the substance is 0 grams.
The substance decays by 500 grams every 0 days.
It takes 500 days for the substance to decay to half its original mass.
