If a sample of radioactive material has a half-life of 8 years then the end of 24 years

 

As the half life = 8 year. So if the initial parent element was 1 then after 8 year the parent element will be 1/2=0.5. So daughter element will be= 1-0.5= 0.5.

After 16 year the parent element will be = 0.5/2=0.25 and the daughter element will be = 1-0.25 = 0.75

After 24 year the parent element will be = 0.25/2=0.125 and the daughter element will be = 1-0.125 = 0.875