If 28.0% of a sample of gallium-66 decays in 4.46 hours, what is the half-life of this isotope (in hours)?

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Explanation:

by simple mathematical rule,

then we know at half life 50% decay occur hence we get

      2.  50% = T 1/2

solving the 2 equations by cross multiplication we will get,

  T 1/2= 7.96 hr

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