question_answer

A radioactive isotope X with half-life \[1.5\times {{10}^{9}}\,\] yr decays into a stable nucleus Y. A rock sample contains both elements X and Y in the ratio 1:15. The age of the rock is:

A) \[3\times {{10}^{9}}\,\,yr\]                  

B) \[6\times {{10}^{9}}\,\,yr\]

C) \[4.5\times {{10}^{9}}\,\,yr\]    

D) \[9\times {{10}^{9}}\,\,yr\]