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M _ N _ T _ S 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 IT WOULD TAKE 5 MINUTES. EACH MACHINE TAKES 5 MINUTES TO MAKE ITS WIDGET. THEREFORE, EACH OF THE 100 MACHINES WOULD HAVE FINISHED MAKING ITS WIDGET IN 5 MINUTES 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 MESSENGER HAS TO HAVE TRAVELED 2 KM. IT DOESN'T MATTER WHAT SPEED THEY WALKED AT. AT THE BEGINNING OF THE PUZZLE, THE LINE IS 1 KM LONG. THE GENERAL IS THEREFORE 1 KM AHEAD OF HIM. THE MESSENGER MUST THEREFORE TRAVEL MORE THAN 1 KM TO REACH THE GENERAL. SINCE THE LINE MOVES 1 KM FORWARD, THE END IS WHERE THE BEGINNING WAS. EVEN IF HE WALKED 1.5 KM TO THE GENERAL, HE ONLY HAS TO WALK 0.5 KM TO GET BACK TO THE END OF THE LINE. IT GOES FASTER GOING BACK, BECAUSE NOW THEY ARE COMING TOWARDS HIM, AND NOT GOING AWAY