ros launch problem

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As I have just started learning Ros with the help of Ros tutorials the problem which i am facing is that according to Ros tutorials link http://www.ros.org/wiki/ROS/Tutorials/UsingRxconsoleRoslaunch when i type roslaunch command in the new terminal it gives me an error that danishraza@ubuntu:~/ros_workspace$ roscd beginner_tutorials roscd: No such package 'beginner_tutorials'

I have Ubuntu 10.04 Lts on my machine and Ros electric.And have already created package beginner_tutorials .