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SSC Sample Paper SSC CGL - Sample Paper-3

  • question_answer
    A and B can do a piece of work in 72 days. B and C can do it in 120 days. A and C can do it in 90 days. In how many days all the three together can do the work?       

    A)  80 days                       

    B)  100 days          

    C)  60 days           

    D)  150 days 

    Correct Answer: C

    Solution :

    \[A+B-72\] days 1 work \[\therefore \] \[A+B\] in day \[\frac{1}{72}\] work Similarly. \[B+C\] in 1 day \[\frac{1}{120}\] work and \[A+C\] in 1 day \[\frac{1}{90}\] work \[\therefore \]      \[2(A+B+C)\,\,1\] day             \[\frac{1}{72}+\frac{1}{120}+\frac{1}{90}\] \[A+B+C\] in 1 day             \[\frac{1}{2}\left( \frac{1}{72}+\frac{1}{120}+\frac{1}{90} \right)\]             \[=\frac{1}{20}\left( \frac{10+6+8}{720} \right)\]             \[=\frac{1}{2}\times \frac{24}{720}=\frac{1}{60}\] work \[A+B+C=\frac{1}{60}\] work = 1 days \[A+B+C=1\] work = 60 days   


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