Cesium-137 is part of the nuclear waste produced by uranium-235 fission. The half-life of cesium-137 is 30.2 years. How much time is required for the activity of a sample of cesium-137 to fall to 25.1 percent of its original value?

Answer 1

ln(100/25.1) = kt
k = 0.693/t_1/2
sUBSTITUTE AND SOLVE FOR t.