Answer :
Final answer:
The number of years required for 28 mg of cesium-137 to decay to 3.5 mg is approximately 120.68 years.
Explanation:
To determine the number of years required for 28 mg of cesium-137 to decay to 3.5 mg, we can use the concept of half-life. The half-life of cesium-137 is 30.17 years, which means that after 30.17 years, half of the initial amount of cesium-137 will have decayed. Using this information, we can calculate the number of half-lives required to reach 3.5 mg from 28 mg. We divide 28 mg by 2 repeatedly until we reach a value close to 3.5 mg. This calculation gives us approximately 4 half-lives. Since each half-life is 30.17 years, we multiply 4 by 30.17 to find that it takes approximately 120.68 years for 28 mg of cesium-137 to decay to 3.5 mg.
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