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Railways Sample Paper RRBs Assistant Loco Pilot and Technician CBT STAGE-I Sample Paper-23

  • question_answer
    A work can be completed by P and Q in 12 days, Q and R in 15 days and R and P in 20 days. In how many days P alone can finish the work?

    A)  10                   

    B)  20

    C)  30       

    D)  60

    Correct Answer: C

    Solution :

    (P + Q)'s1 day's work\[=\frac{1}{12}\]                 ...(i) (Q+R)'s1 day's work\[=\frac{1}{15}\]                   ...(ii) (R + P)'s 1 day's work\[=\frac{1}{20}\]                ...(iii) Adding all three equations, we get 2 (P+Q+R)'s 1day's work \[=\frac{1}{12}+\frac{1}{15}+\frac{1}{20}=\frac{5+4+3}{60}=\frac{12}{60}=\frac{1}{5}\] \[\because \](P + Q + R)'s 1 day's work \[\frac{1}{10}\]      ...(iv) \[\therefore \]P's 1 day's work = Eq. (iv) - Eq.(ii) \[=\frac{1}{10}-\frac{1}{15}=\frac{3-2}{30}=\frac{1}{30}\] \[\therefore \]P alone will complete the work in 30 days.


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