1. 2b. Assume you have a sample of atoms with a half-life of 0.5 second. Approximately how much (in %) of the original sample will be around after 3.5 seconds? * Choose the answer closest to the exact value.

•  0.1%
•  0.3%
•  1%
•  3%
•  10%
•  30%
•  100%

2c. Potassium-40 decays to Argon-40 with a half-life of 1.25 billion years old. If at the formation of the Earth we had 100% Potassium-40 and 0% Argon-40, what should be ratio of Potassium-40 / Argon-40 on the Earth today? * choose closest answer

•  0.05
•  0.09
•  .40
•  0.91
•  1.1
•  2.5
•  3.6
•  11.5
•  20
•  100