Rb-84 is used to monitor cardiac output and has a half life of 33 days. It would take approximately 165 days for a 1.000 mg sample of Rb-84 to decay to 0.063 mg.

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Quizplus · Accepted Answer

Rb-84 has a half-life of 33 days, but to decay from 1.000 mg to 0.063 mg (which is approximately 1/16 or 2^-4 of the original amount), it would take 4 half-lives. 4 half-lives x 33 days/half-life = 132 days, not 165 days.

Rb-84 Is Used to Monitor Cardiac Output and Has a Half