# At a given instant there are 25 % undecayed radioactive nuclei in a same. After 10 sec the number of undecayed nuclei reduces to 6.25 %, the mea

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At a given instant there are 25 % undecayed radioactive nuclei in a same. After 10 sec the number of undecayed nuclei reduces to 6.25 %, the mean life of the nuclei is.
A. 14.43 sec
B. 7.21 sec
C. 5 sec
D. 10 sec

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