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Problem 8 - Olympiad

A radioactive nucleus decays by two parallel modes with half-lives 4 h and 6 h. The effective half-life of the sample is

Correct: A

λ_eff = λ₁ + λ₂ = ln2/4 + ln2/6 = ln2(5/12). T½_eff = ln2/λ_eff = 12/5 = 2.4 h.