Calculating disk seek times
@tonny, 
     I am also found this example from a book, I think the number 6 is missed after the number 40 in the example. The correct order is 10, 22, 20, 2, 40, 6 and 38.
So if it starts from cylinder 20,
You can write it as, -> (20), 10, 22, 2, 40, 6, 38
                     -> (20-10)+(10-22)+(22-2)+(2-40)+(40-6)+(6-38)
                     ->  10+12+20+38+34+32
                     -> 146.
So seek time is = 146*6
                  876 ms.