Using the half - life value of cobalt Given, the amount of cobalt - 60 left after 15 years would be 1.25 grams.
Given :
- Half - life of Cobalt - 60 = 5 years
Half - life defines the amount of time taken for a radioactive substance to Decay to half of it's original size ;
After 5 years ;
Amount of cobalt left = 10 / 2 = 5 grams
After 10 years ;
Amount of protactinium left = 5 / 2 = 2.5 grams
After 15 years ;
Amount of protactinium left = 2.5 / 2 = 1.25 grams
Therefore, the amount of cobalt - 60 left after 15 years would be 1.25 grams.
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