PL/SQL :: How To Truncate Data In Table Partitions

I couldn't either DROP or TRUNCATE the table partitions that were created. Here are the DDLs and DMLs I'm using. 

Create table student(no number(2),name varchar(2)) partition by range(no) (partition 
p1 values less than(10), partition p2 values less than(20), partition p3 values less     
than(30),partition p4 values less than(40)); 
Insert into student values(1,'a');
Insert into student values(11,'b');
Insert into student values(21,'c');
Insert into student values(31,'d'); 

When I do the following query, it returns data.

SELECT * FROM STUDENT PARTITION(p1); 

But, when I try to perform any of the following queries, it says invalid partition name. 

ALTER TABLE STUDENT DROP PARTITION p4;
ALTER TABLE STUDENT TRUNCATE PARTITION p3;

I am using Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit