Answers

2016-03-02T15:22:39+05:30
( I don't know exact answer. Just bny guessing )
we can use inverse variation method
  speed (kmph)       distance (km)
        21                         40 + x
       15                               x

21 * (40 + x)   =  15 x
840 + 21x       = 15 x
 840                = -6x
    x      = 140 km 

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