9. A radioactive sample with an initial mass of 35 mg has a half-life of 3 days. Which of the following equations models the exponential decay for time, t, in days? (2) a. с. A = 35(2) A = 35 b. d. A = 35(2) A = 35 1/2

Cesium-137 has a half-life of about 30 years. If we begin with 200 mg of cesium-137, will it take more or less than 230 years until only 1 milligram remains?

The half-life of a radioactive material is about 34.2 years. How much of the material is left after 20 years?

A radiation safety officer is working with 112 grams of a radioactive substance. After 17 days, thesample has decayed to 80 grams. Rounding to fivesignificant digits, write an exponential equationrepresenting this situation. To the nearest day, whatis the half-life of this substance?