The half-life of iodine-131 is 8 days. Chan Hee examines two samples of iodine-131.Sample 1: 10 gSample 2: 20 gWhat can Chan Hee expect to observe about the samples after 16 days?

After 16 days, two 8-day half-lives have passed. Each sample retains one-half after the first half-life and one-half of that amount after the second, so one-fourth remains and three-fourths has decayed. Therefore, three-fourths of each sample will have undergone radioactive decay.

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