The​ half-life of radium is 1690 years. If 80 grams are present​ now, how much will be present in ​730 years?

Answer 1

1690 years = half life

after 730 years what's left?

start with 80 grams

more than 40, maybe 50 or so?

rough guess

general formula is

A=Pe^rt

1/2 = e^1690r where r = rate of decay which is negative

1/2 = e^1690r

ln(.5) = 1690r

r = ln(.5)/1690 =-.69/1690 = -.00041

A=80e^-.0041(730)

A =59.3 grams