Finding the Mass of a Meter Stick without a Scale

Step 1 of this lab was to describe what steps I would take to find the mass of the meter stick without the use of a scale, but with the use of a 100g lead weight.
I would use these equations:
Torque = Lever Arm X Force
(I would later realize that I needed W=Mg, but it was not in my original plan).

My Plan:
Find the length of each lever arm when the meter stick is balanced with the weight on one side, then use the torque equation to find the value of the force on the other side.

My Reasoning:
Left Force(weight) X Left Lever Arm = Right Force(unknown) X Right Lever Arm
This equation shows that when the stick is balanced on a fulcrum with the 100g weight on one side, the clockwise and counter-clockwise torques will be equal.  Therefore, solving for x should produce the mass of the meter stick.

My next step was to execute my plan and find the mass of the meter stick with the given materials.  First, I sketched a drawing of what the system should look like.  Then I placed the meter stick on the edge of a table, and placed the weight on one end.  One error I encountered while setting the experiment up was that I placed the weight closer to the fulcrum, when I should have placed it all the way to the side, increasing the lever arm length.  I then measured the length of each lever arm.  The side with the weight had a 30 cm lever arm, while the other side had a 20 cm lever arm.  One mistake I made during the measuring process was that I measured the entire right side and took that as the lever arm.  That would indicate that all the force acts at the very tip of the meter stick, which is not true.  I had to re measure from the fulcrum to the center of mass, because that is where the force acts to pull the ruler down.

My next step was to set up my numerical equation.  I had to remember to use w = mg to convert all of my measurements to the proper units, and also to use 9.8 N as the measurement for gravity, since we are in the real world and can use calculators.  My equation was:
                     
 .98 N X 30 = 20X

In the equation, the X on the right side represents the force on the right side of the meter stick.  I then solved for X and the answer I got was 1.47 N.  Since the prompt asked for the MASS of the meter stick, I needed to convert the answer to kilograms.  Once I did this, my answer was 147 kilograms, which is very close to the actual mass of the meter stick.