2 gaps between 1st to 3rd floor. hence, 4/2=2 minutes per gap.  Moving from 2nd to 5th floor, 3 gaps -\textgreater{} 3 gaps x 2 minutes per gap = 6 minutes. 
George takes 4 minutes to go from 1st floor to 3rd floor. He just realised that he forgot his water bottle on the 5th floor. He is now on the 2nd floor. How long would it take him to get his watter bottle? 

1) 4 minutes 
2) 5 minutes 
3) 6 minutes 
4) 8 minutes 
5) None of the above. 