Railways Technical Ability Instrument Mechanical Question Bank Instrument Mechanical

  • question_answer Estimated time T, and variance of the activities 'V on the critical path in a PERT new work are given in the following table:
    Activity \[{{\mathbf{T}}_{\mathbf{e}}}\] (days) V \[{{\left( \mathbf{days} \right)}^{\mathbf{2}}}\]
    a 17 4
    b 15 4
    c 8 1
    The probability of completing the project in 43 days is:

    A) 15.6%              

    B) 50.0%

    C) 81.4%              

    D) 90.0%

    Correct Answer: C

    Solution :

    \[\sum{{{T}_{e}}}=17+15+8=\]40 days \[\sum{V=4+4+1=9}\] \[\sigma =\sqrt{\sum{V}}=\sqrt{9}=3\] \[{{T}_{s}}\,=\] 43 days \[z=\frac{{{T}_{s}}-{{T}_{e}}}{\sigma }=\frac{43-40}{3}=1\] For z = 1, P = 0.8143 or 81.43%

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