The​ half-life of radium is 1690 years. If 80 grams are present​ now, how much will be present in 920 ​years?

Question

The​ half-life of radium is 1690 years. If

80

grams are present​ now, how much will be present in

920

​years?

Answer 1

1/2 =e^1690r

ln.5 =1690r

r = (ln.5)/1690 = about -4.1015

A= 80e^920(-4.1015)

= about 54.855 grams after 920 years

in 1690 years 40 grams are left

in 920 years about 55 grams are left