radium has a half life of 1660 years. If the initial amount of radium is 200 grams, how much will remain in 500 years?

Amount remaining = (original amount) x (2)^-(years/1660)Amount remaining = (200) x (2)^-(500/1660)= (200) x (2)^-(0.3012)= (200) x (0.8116) = 162.3 grams (rounded)