Question

The table below shows the initial and final masses of a radioactive material whose half-life is 15 years.

Initial mass (in kilograms): 0.8
Final mass (in kilograms): 0.05

Based on the table, which of these conclusions is correct?

A.) The material decayed from 0.8 kilograms to 0.05 kilogram in 60 years.
B.) The material decayed from 0.8 kilograms to 0.05 kilogram in 30 years.
C.)The mass of the material was 0.1 kilograms after four half lives.
D.) The mass of the material was 0.1 kilograms after five half lives.

Answer 1

A

Step-by-step explanation:

Initial mass is 8. The half-life is 15 years.

1st half life=.8/2=.4

2nd half life=.4/2=.2

3rd half life=.2/2=.1

4th half life=.1/2=.05

For each half life that it took it to go from .8 to 0.05, you add 15 years since that is the half life of the substance. 4*15=60.

So, the answer is A. The material decayed from 0.8 kilograms to 0.05 kilogram in 60 years.

Answer 2

A

Step-by-step explanation:

1 half-life = .4 kg = 15 years

2 half-life = .2 kg = 30 years

3 half-life = .1 kg = 45 years

4 half-life = .05 kg = 60 years