Multiple Choice Question: A radioactive substance is decaying according to the formula x = ke^(-0.2t) where x is the amount of material remaining after t years and k is the initial amount.

A radioactive substance is decaying according to the formula x = ke^-0.2t where x is the amount of material remaining after t years and k is the initial amount. Find the half-life of this substance.

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Orphaned Multiple Choice Questions (MCQ) due to changes of exam system.

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