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 60 - Sample remaining (7) 40 30 - 20 - . . . . . . . . . . . 10 - 0 10 20 30 40 50 60 70 80 90 100 130 120 130 140 150 160 170 180 190 Time (days) If the initial sample is 9.00 g. what mass of the original iridium-192 remains after 85 days? mass remaining: 4.05 g Estimate the half-life of the radioisotope. half-life: 75 days How many days would it take for three-fourths of the sample to decay? 56.25 days time