How private IP address is determined?
&quot;The questioner asked my why private IP address is determined in such range&quot;
IMO a good answer is &quot;Because it has been established in RFC-1918; which is a &quot;Best Current Practice&quot; RFC :-)
The three ranges allow private networks to &quot;resemble&quot; the class A-B-C subdivision (and probably this is what the questioner wanted to hear from you). See older RFC791: .... To provide for flexibility in assigning address to networks and
allow for the  large number of small to intermediate sized networks
the interpretation of the address field is coded to specify a small
number of networks with a large number of host, a moderate number of
networks with a moderate number of hosts, and a large number of
networks with a small number of hosts..... Also see Wikipedia Classful network for more details / references.
The reasons for the particular numbers are not well known (and are only interesting from a historical-folklore point of view), and probably the main criteria was to use address spaces that were free/unused at the moment.

10.x.x.x comes from the old ARPANET and is easy to remember
172.x.x.x was marked by IANA as &quot;Special purpouse&quot; block of IP addresses
192.168.x.x was used by Sun in its workstations (?!?)