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                   23512 Points
                   Joined July 2007
                
               
			  
			  
             
            
             Now can you answer this one???
A military column of 1 km length marches with a constant speed of 6 kilometers per hour. A courier from the back of the column is sent to the head of the column by bike to deliver a massage. Arrived at the front, he 
instantly returns. When he returns again at the back, the column has travelled a distance of 1 km since the start of his errand. The courier drove with constant speed. 
How fast did the courier bike?