Q. 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.

• 1st milestone = xy
  2nd milestone = yx
  3rd milestone = x0y or y0x
  Since the first 2 values are two digits, the average speed can't be greater than 100.
  Thus difference between 2nd and 3rd value is also less than 100.
  Thus third milestone is in 100's
  Thus x = 1
  Now checking for possibility of y: y = 6
  
  1st milestone = 16
  2nd milestone = 61
  3rd milestone = 106
  Average speed = 45 mph
• 10 years agoHelpfull: Yes(1) No(1)