Shell Scripting : "let not found" solved

I was recently scripting in UNIX and bumped across one problem.

I had used the following code in my script.

let "result=no1+no2"

And I got the error - "let not found"

But the solution is simple.

It seems that the shell is using dash, instead of bash. Hence, reconfigure the dash.
sudo dpkg-reconfigure dash
<password>

Then, when the option to reconfigure comes up, select "No", ie do not make dash the default shell.

PROBLEM SOLVED!!!