The percentage of the radioactive isotope left is 25.0000%.
What is the half life?
The half life of a radioactive isotope is the time that will elapse before only half of the number of original isotopes will remain.
Now;
We are told that;
Half life (t1/2) = 55 days
Time taken (t) = 115 days
Ratio of isotope remaining = N/No
Thus;
N/No = (1/2)^t/t1/2
N/No = (1/2)^115/55
N/No = (1/2)^2
N/No =1/4
Hence, the percentage = 1/4 * 100/1 = 25.0000%
Learn more about half life of an isotope:https://brainly.com/question/16387602
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