Find the placement for 4th mass

[leighkla]

Homework Statement

a meter stick is initially balanced on a fulcrum at its midpoint. you have four identical masses. three of them are placed at the following locations: 25 cm, 45 cm, and 90 cm. where should the fourth mass be placed in order to balance the meter stick?

Homework Equations

T=rxF ; m1r1+m2r2=m3r3=m4r4
each mass is identical but the problem does not give a mass.

The Attempt at a Solution

 

[haruspex]

Please fill in the template. List any equations/principles you have been taught which you suspect are relevant and show your thinking so far.

 

[haruspex]

each mass is identical but the problem does not give a mass.

Don't let that stop you. Just fill in the masses as an unknown m and trust that if there is no mistake in the question then m will disappear later.

m1r1+m2r2=m3r3=m4r4

Is there a typo in there?
What values for r1, etc. should you plug in?