Static Equilibrium-Balancing Forces and Torque

[phizics09]

Homework Statement

Two children of masses 45 kg and 30 kg are playing on a teeter-totter of length 4.0m and mass 30.0kg, pivoted at its centre. The heavier child sits 1.75 m from the centre of the teeter-totter that is 0.50 m from the ground. a) What torque does the teeter-totter apply to each of its sides? With this knowledge, how could you simplify any further calculations.

Homework Equations

T=r x Fsin(theta)

The Attempt at a Solution

The example says:
T=rF sin (theta)
T=(1.0 m)(30.0 kg)(9.8 N/kg)
t-t  147 N·m

I don't understand where the one metre is coming from.
Can anyone help me?


 

[sandy.bridge]

The question is too vague to answer. It doesn't specify the coordinates of the other child.