A Sample of a Radioactive Isotope Decays at a Rate

question 33

Multiple Choice

A sample of a radioactive isotope decays at a rate of 988 disintegrations per minute. Exactly 85 minutes later the decay rate of the sample is 251 disintegrations per minute. What is the half-life of this isotope?

• A) 1.61×10 ^{- 2} min
• B) 2.32×10 ^{- 2} min
• C) 15.0 min
• D) 43.0 min
• E) none of these

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