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NTSE Sample Paper NTSE SAT Practice Test-14

  • question_answer
    An aeroplane flies along the four sides of a square at the speeds of 200 kmph; 400 kmph; 600 kmph and 800 kmph. The average speed of the plane around the field is

    A) 500 kmph         

    B)        480 kmph

    C) 384 kmph    

    D)        395 kmph

    Correct Answer: C

    Solution :

    [c] Let each side be x km. so that total distance to be travelled = 4x \[\Rightarrow \]Total time \[=\frac{x}{200}+\frac{x}{400}+\frac{x}{600}+\frac{x}{800}\] \[=\frac{25x}{2400}\] Let y be the average speed. \[\therefore \,\,\frac{4x}{y}=\frac{25x}{2400}\,\,so\,\,y=2400\times \frac{4}{25}=384.\]   


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