Mastering Half-Life Calculations and Graphing Decay

A radioactive substance has a half-life of 5 years. If you start with 80 grams, how much will remain after 15 years?

• 40 grams

• 10 grams

• 5 grams

• 20 grams

The half-life of a certain medication in the body is 3 hours. If a patient takes a 200 mg dose, how much of the medication will be left in the body after 9 hours?

• 25 mg

• 100 mg

• 50 mg

• 75 mg

A certain isotope has a half-life of 10 days. If you have 50 mg of the isotope, how much will be left after 30 days?

• 3.125 mg

• 12.5 mg

• 6.25 mg

• 25 mg

Graph the exponential decay of a substance with a half-life of 4 days, starting with 100 grams. What will the graph look like after 12 days?

• 25 grams

• 12.5 grams

• 50 grams

• 75 grams

A culture of bacteria decreases by half every 2 hours. If you start with 1,000 bacteria, how many will be present after 8 hours?

• 250

• 62

• 125

• 500

The half-life of a certain chemical is 6 months. If you have 120 mg of the chemical, how much will remain after 1.5 years?

• 30 mg

• 5 mg

• 60 mg

• 15 mg

Create a graph showing the decay of a substance with a half-life of 8 hours, starting with 200 grams. How much will remain after 24 hours?

• 100 grams

• 50 grams

• 10 grams

• 25 grams

A certain element has a half-life of 15 years. If you have 160 grams, how much will remain after 45 years?

• 20 grams

• 80 grams

• 30 grams

• 5 grams

If a radioactive material has a half-life of 12 years, how long will it take for a sample to decay to 25% of its original amount?

• 12 years

• 36 years

• 24 years

• 48 years

Graph the decay of a substance with a half-life of 2 days, starting with 50 grams. What will the amount be after 10 days?

• 3.125 grams

• 1.5625 grams

• 25 grams

• 12.5 grams