SQL Developer

I'm on Oracle 11.2

In SQL Developer, I'm having hard time executing a SQL with a bind variable. Below is the test table.

create table TEST1 (TYP varchar2(3), NUM number(30,18));  
insert into TEST1 values ('TTT', 45.15168794137111);  
commit;  

Then I execute the below query and it returns no results. Why?

VARIABLE P1 number;  
EXEC :P1 := 45.15168794137111;  
select * from TEST1 where NUM = :P1;  

The above works in SQL Plus.