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8 : 1 5 Clue
THE SON WILL CATCH UP WITH HIS FATHER IN 10 MINUTES. IN 10 MINUTES, THE SON WOULD HAVE TRAVELED HALF THE DISTANCE, SINCE HIS TOTAL TRAVELING TIME IS 20 MINUTES. THE FATHER STARTED 5 MINUTES EARLIER THAN THE SON, SO HE WOULD HAVE TRAVELED FOR A TOTAL OF 15 MINUTES WHEN HIS SON REACHED HIM. THEREFORE, THE FATHER WOULD HAVE ALSO TRAVELED HALF THE DISTANCE IN 15 MINUTES THE DIFFERENCE BETWEEN THE REAL TIME AND THE TIME OF THE MIRROR IMAGE IS TWO HOURS AND TEN MINUTES (TWO AND A HALF HOURS, MINUS THE TWENTY MINUTES OF CYCLING). THEREFORE, THE ORIGINAL TIME ON THE CLOCK AT HOME THAT MORNING COULD ONLY HAVE BEEN FIVE MINUTES PAST SEVEN: THE DIFFERENCE BETWEEN THESE CLOCKS IS EXACTLY 2 HOURS AND TEN MINUTES (NOTE THAT ALSO FIVE MINUTES PAST ONE CAN BE MIRRORED IN A SIMILAR WAY, BUT THIS IS NOT IN THE MORNING!). CONCLUSION: THE BOY REACHES SCHOOL AT FIVE MINUTES PAST SEVEN PLUS TWENTY MINUTES OF CYCLING, WHICH IS TWENTY-FIVE MINUTES PAST SEVEN!.. HE LEAVES HIS HOUSE AT 7.15 AND REACHES SCHOOL AT 8.15. FROM THE MACHINE AND TRACTOR STATION TO THE RAILROAD STATION IS 1/3 - 1/4 = 1/12 OF THE WAY. BORIS WALKS IT IN 5 MINUTES, SO THE WHOLE TRIP TAKES 1 HOUR. ONE-FOURTH OF THE WAY IS 15 MINUTES. SO HE LEAVES HIS HOUSE AT 7:15 AND REACHES SCHOOL AT 8:15 THE TRAIN IS ABOUT TO LEAVE AND YOU WILL NOT BE ABLE TO CATCH THE TRAIN. THE AMOUNT OF TIME TAKEN TO TRAVEL TO THE HALFWAY POINT AT 15 MILES AN HOUR IS THE SAME AMOUNT OF TIME TAKEN TO REACH THE TRAIN STATION WHEN TRAVELLING TO THE RAILROAD STATION AT 30 MILES AN HOUR. FOR EXAMPLE, LET'S ASSUME THAT THE DISTANCE TO TRAVEL IS 30 MILES. WHEN TRAVELLING AT 30 MILES AN HOUR, IT TAKES 1 HOUR. WHEN TRAVELLING AT 15 MILES AN HOUR, IT WILL ALREADY TAKE 1 HOUR TO REACH THE HALFWAY POINT