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Railways Sample Paper RRB (Group D) Sample Test Paper-8

  • question_answer
    An aeroplane flies along the four sides of a square at the speeds of 200, 400, 600 and 800 km/h. find the average speed of the plane around the field.

    A)  384km/h

    B)         370km/h

    C)  368 km/h         

    D)  None of these

    Correct Answer: A

    Solution :

    [a] Let each side of the square be x km and let the average speed of the plane around the field be y km/h. Then, \[\frac{x}{200}+\frac{x}{400}+\frac{x}{600}+\frac{x}{800}=\frac{4x}{y}\] \[\Rightarrow \,\,\,\frac{25x}{2400}=\frac{4x}{y}\Rightarrow y=\left( \frac{2400\times 4}{25} \right)=384.\] \[\therefore \]Average speed = 384 km/h.


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