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Railways R.R.C. (Jabalpur) Solved Paper Held on 2nd Shift 9-11-2014

  • question_answer
    'A' takes 10 days less than the time taken by 'B' to finish a piece of work. If both 'A' and 'B' can do it in 12 days, then the time taken by 'B' alone to finish the work is?

    A) 27 days            

    B) 20 days

    C) 30 days

    D) 25 days

    Correct Answer: C

    Solution :

    Let the time taken by *B' alone to finish work is x days.                            Then, the time taken by 'A' alone to finish the work is \[(x-10)\]days. Now, \[\frac{1}{x}+\frac{1}{x-10}=\frac{1}{12}\] \[\frac{x-10+x}{x(x-10)}=\frac{1}{12}\] \[24{{x}^{2}}-120={{x}^{2}}-10x\]             \[{{x}^{2}}-34x+120=0\] On solving,        x=30, 4 Hence,              x=30 days


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