understanding elapsed_time in v$sql

Hello Oracle Gurus,

Elapsed_time in v$sql=CPU_TIME + APPLICATION_WAIT_TIME + CONCURRENCY_WAIT_TIME + CLUSTER_WAIT_TIME + USER_IO_WAIT_TIME + PLSQL_EXEC_TIME+ JAVA_EXEC_TIME

1.i sometimes see that elapsed_time does not add to the sum of above things..why does that happen and where do i find the missing time of elapsed time ?

2.Also i see in Sql monitoring OEM it sometime shows "other" in "Database time"...which is not in v$sql.

3. Is last_active_time - last_load_time always equal to Elapsed_time ? if not does it include non-idle wait events like '