A man has to get air-mail. He starts to go to airport on his motorbike. Plane comes early and the mail is sent by a horse-cart. The man meets the cart in the middle after half an hour. He takes the mail and returns back, by doing so, he saves twenty minutes. How early did the plane arrive?

• 10min:assume he started at 1:00,so at 1:30 he met cart. He returned home at 2:00.so it took him 1 hour for the
  total jorney.by doing this he saved 20 min.so the actual time if the plane is not late is 1 hour and 20 min.so the actual
  time of plane is at 1:40.The cart travelled a time of 10 min before it met him.so the plane is 10 min early.
• 12 years agoHelpfull: Yes(1) No(7)
• It is impossible to know how early the plane was, only that it was early. If the plane had arrived a whole day early, lets say, but the cart was extremely slow, the distance that the cart had travelled in that time may cut 10 minutes of the motorbikes journey to the airport and thus satisfy the criteria. One needs to know the speed of the cart to know how early the plane was. Unless by in the middle they met in the precise middle, that is.
• 8 years agoHelpfull: Yes(1) No(0)