Calculating disk seek times I have  a system where disk requests come to a disk drive for cylinders in the order 10, 22, 20, 2, 40, and 38 at a time when the disk drive is reading from cylinder 20.  The seek time is 6ms per cylinder.  I have to find total seek time if the disk scheduling algorithm is First-Come-First-Serve (FCFS).

To find the answer I used a formula:

total seek time=0.254*sqrt(d)(for each cylinder and sum them)

But that gave the incorrect result.
What formula(s) should I be using to handle questions like this?
@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.