the problem reproduces even on 11.2.0.1.2. You have accidentally not given the right table name/alias in the hint for the second example. This is why the optimizer did not honour your hint:

should be :

/*+ index(t1xx t1_range) */
instead of:
/*+ index(t1 t1_range) */

Regards,
Martin

I tested it on 11.2 and it seems to be fixed in 11.2.

See my test (I changed the name of t1 to t1xx)

SQL> startup force
ORACLE instance started.
Total System Global Area 1068937216 bytes
Fixed Size                  2220200 bytes
Variable Size             977276760 bytes
Database Buffers           83886080 bytes
Redo Buffers                5554176 bytes
Database mounted.
Database opened.
SQL>
SQL> connect scott/regit
Connected.
SQL> set line 200
SQL> set pagesize 0
SQL> alter session set optimizer_use_sql_plan_baselines = false
  2  ;

Session altered.

SQL> select
    small_vc
from
    t1xx
where
    scattered = 10
and clustered between (select 40 from dual)
              and     (select 41 from dual)  2    3    4    5    6    7    8  ;
0000020011
0000020031
0000020051
……..
0000020071

50 rows selected.

SQL> select * from table(dbms_xplan.display_cursor)
  2  ;
SQL_ID  bsvcwujxd02p6, child number 0
-------------------------------------
select     small_vc from     t1xx where     scattered = 10 and
clustered between (select 40 from dual)               and     (select
41 from dual)

Plan hash value: 1241395774

---------------------------------------------------------------------------------------
| Id  | Operation                   | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |         |       |       |    17 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| T1XX    |     5 |   140 |    13   (0)| 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | T1_EQUI |     9 |       |     9   (0)| 00:00:01 |
|   3 |    FAST DUAL                |         |     1 |       |     2   (0)| 00:00:01 |
|   4 |    FAST DUAL                |         |     1 |       |     2   (0)| 00:00:01 |
---------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - access("SCATTERED"=10 AND "CLUSTERED">= AND "CLUSTERED"= AND "CLUSTERED" select
    /*+ index(t1 t1_range) */
    small_vc
from
    t1xx
where
    scattered = 10
and clustered between (select 40 from dual)
              and     (select 41 from dual)  2    3    4    5    6    7    8    9  ;
0000020011
0000020031
…..
0000020951
0000020971
0000020991

50 rows selected.

SQL> select * from table(dbms_xplan.display_cursor) ;
SQL_ID  da0446kv1h1v8, child number 0
-------------------------------------
select     /*+ index(t1 t1_range) */     small_vc from     t1xx where
  scattered = 10 and clustered between (select 40 from dual)
   and     (select 41 from dual)

Plan hash value: 1241395774

---------------------------------------------------------------------------------------
| Id  | Operation                   | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |         |       |       |    17 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| T1XX    |     5 |   140 |    13   (0)| 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | T1_EQUI |     9 |       |     9   (0)| 00:00:01 |
|   3 |    FAST DUAL                |         |     1 |       |     2   (0)| 00:00:01 |
|   4 |    FAST DUAL                |         |     1 |       |     2   (0)| 00:00:01 |
---------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - access("SCATTERED"=10 AND "CLUSTERED">= AND "CLUSTERED"= AND "CLUSTERED"<=))


24 rows selected.

Regards Hans-Peter

I am afraid revelations like these are making me “atheist” about Oracle :)
On a serious note, thanks for sharing this.