Question

Arianna finds some fossil bones while digging in her backyard. Could they be dinosaur bones? Using carbon dating, she determines that 3% of the original radioactive carbon-14 is still radioactive. (The rest has decayed to nitrogen-14.) Approximately how many half-lives have occurred?
The half-life of carbon-14 is 5,730 years. This means that the animal died approximately _____ years ago.

Answer 1

Answer:

- approximately 5 half lives

- 28,650 years ago

Explanation:

After 1 half life:

50% gone, total gone = 50% and the amount that is left = 50%

After 2 half lives:

25% gone, total gone = 50 + 25 = 75% and the amount that is left = 25%

After 3 half lives:

12.5% gone, total gone = 87.5% and the amount that is left = 12.5%

After 4 half lives:

6.25% gone, total gone = 93.75% and the amount that is left = 6.25%

After 5 half lives:

3.125% gone, total gone = 96.875% and the amount that is left = 3.125%

Therefore, we can say that nearly 5 half-lives have occurred and the animal died approximately (5 x 5730 = ) 28,650 years ago.

Answer 2

Answer: 5

28,650

Explanation: