The half life of a radioactive element is 23 days. How long until 21% of the initial amount remains? Include units in your answer?

Question

The half life of a radioactive element is 23 days. How long until 21% of the initial amount remains? Include units in your answer?

Answer 1

0.21 = (0.5)^t/23

 

t is in days

 

log(0.21) = (t/23)log(0.5)

 

t = 23 log(0.21) / log(0.5) ≅ 51.785 days

 

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