Update field value to decimal

Suppose there is a field salary and the value is 9125462, the rightmost number(2) indicates the number of values after decimal. We have to update the same for all records. Eg for above number 9125.46 should be updated, for 452861, it should be updated as 4528.6. How will you do this?

SQL> SELECT * FROM XXX;

A
---------
9125462
452861

SQL> UPDATE XXX
2 SET A = (TRUNC(A/100)||'.'||MOD(A,100)) ;

2 rows updated.

SQL> SELECT * FROM XXX;

A
---------
91254.62
4528.61

use this in ur updation
select decode(substr(&num,length(&num)),2,substr(&num,1,length(&num)-1)/100,1,substr(&num,1,length(&num)-1)/10,3,substr(&num,1,length(&num)-1)/1000) from dual