If a radioactive substance's half-life is 20 years, how much of a 40-gram sample will be left after 60 years? A. 5 grams B. 10 grams C. 20 grams D. 30 grams

Respuesta :

60 years is three half life for the substance, so 40*1/2^3=5

Answer:

c. 20

Explanation: