Erlang shell problem

Im new to Erlang. Im using Erlang on Ubuntu 10.10. I typed erl to start the erlang shell (Eshell V5.7.4). The shell starts. But, if i type some expression in the shell like say 20+30 and hit enter im back to 1>, and the result of the expression is not shown.

What could be causing this problem ?

Please Help Thank You.