A car is travelling at a uniform speed. The driver sees a milestone showing a 2-digit number. After travelling for an hour the driver sees another milestone with the same digits in reverse order. After another hour the driver sees another milestone containing the same two digits. What is the average speed of the driver.

One Answer on this Question

1. Let 10’splace digit is x and unit’s place digit y

   First milestone : 10x+y
   Second milestone : 10y+x
   Third milestone: 100x+y

   Since the speed is uniform so
   Distance covered in first Hr = Distance covered in Second Hr
   (10y+x)-(10x+y) = (100x+y)-(10y+x)
   After solving, we get —-> y=6x but since x and y are digits so only possible combination is x=1 and y=6,
   So average speed = 45 KM/HR

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