Posted by Charley on .
The isotype caesium 137, which has a half life of 30 years, is a product of nuclear power plants. How long will it take for the amount of this isotype in a sample of caesium to decay to onesixteenth of its original amount?
first half life 1/2
second 1/4
third 1/8
fourth 1/16
so how long is four halflives?
120 years
30=1/2
60=1/4
90=1/8
120=1/16

chemistry 
Steve,
try the equation No= 1/2^n