Radioactivity and radioactive isotopes have the potential for both benefiting and harming living organisms. One use of radioactive isotopes is in radiation therapy as a treatment for cancer. Cesium-137 is sometimes used in radiation therapy. A sample of cesium-137 was left in
an abandoned clinic in Brazil in 1987. Cesium-137 gives o! a blue glow because of its radioactivity. The people who discovered the sample were attracted by the blue glow and had no idea of any danger. Hundreds of people were treated for overexposure to radiation, and four people died.
If 12.5 grams of the original sample of cesium-137 remained after 90.69 years, what was the mass of the original sample?