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Iridium-192 is one radioisotope used in brachytherapy, in which a radioactive source is placed inside a patient's body to treat cancer. Brachytherapy allows the use of a higher than normal dose to be placed near the tumor while lowering the risk of damage to healthy tissue. Iridium-192 is often used in the head or breast. Use the radioactive decay curve of iridium-192 to answer the three questions. 100 90 80 70 60- Sample remaining (%) 50 . 40 30 20 - 10- 0 T 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 Time (days) If the initial sample is 2.25 g, what mass of the original iridium-192 remains after 130 days?

If the initial sample is 2.25 g, what mass of the original iridium-192 remains after 130 days? mass remaining: g Estimate the half-life of the radioisotope. half-life: days How many days would it take for one-third of the sample to decay? time: days