Divvy a hard disk

What is the general rule for a divvy of a hard disk, I know that the boot is 20 megs swap is times 2 of ram. I am learning unix
for the first time and at work i cant get this divvy thing down pat yet.
boot 1 to 19999
swap 20000 to 122499 (512 megs of ram)
root 122500 to ?
u ?
u2 ?

lets say this is on a 10 gig hard disk. I would really like some help with this
And how do i under stand blocks from megs?
This might help me a little better

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