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RAJASTHAN PMT Rajasthan - PMT Solved Paper-1999

  • question_answer
    Half life of radioactive element is 30 days, After 90 days percentage decayed of the element will be :                   

    A)  92.15%                

    B)         87.5%     

    C)  47%                      

    D)         18.5%    

    Correct Answer: B

    Solution :

    Remaining quantity \[N={{N}_{0}}{{\left( \frac{1}{2} \right)}^{t/{{t}_{1/2}}}}\] \[{{N}_{0}}{{\left( \frac{1}{2} \right)}^{90/30}}\] \[N=\frac{{{N}_{0}}}{8}\] Decayed amount \[={{N}_{0}}\frac{{{N}_{0}}}{8}\] \[=\frac{7{{N}_{0}}}{8}=\frac{7}{8}\times \]100=87.5%


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