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Railways Sample Paper RRB (Group D) Sample Test Paper-11

  • question_answer
    A train overtakes two persons who are walking in the same direction in which the train is running, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train (in metres):

    A)  72                   

    B)  45

    C)  54                   

    D)  50

    Correct Answer: D

    Solution :

    [d] Let the length of train be x km and its speed by kmph. \[\therefore \frac{x}{y-\,2}=\frac{9}{3600}=\frac{1}{400}\]                     ? (i) \[\frac{x}{y-\,4}=\frac{10}{3600}=\frac{1}{360}\]                     ... (ii) By dividing equation (i) by (ii), \[\frac{y-\,4}{y-\,2}=\frac{360}{400}=\frac{9}{10}\] \[\Rightarrow 10y-\,40=9y-\,18\] \[\Rightarrow y=40-\,18=22\] From equation (i), \[\frac{x}{22-\,2}=\frac{1}{400}\] \[\Rightarrow x=\frac{1}{20}\,\,km=\frac{1000}{20}=50\,\,metre\] Alternate Method: Let Speed of train be x km/h According to question \[(x-2)\,\,\frac{5}{18}\times 9=(x-y)\,\,\frac{5}{18}\times 10\] \[9x-\,18=10x-\,40\]        \[x=22\,\,km/h\] \[\operatorname{Re}quired\,\,lenght=(22-\,2)\frac{5}{18}\times 9=50\,\,m\]


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