physics
posted by john on .
the magnitude of the tongue produced by a 3.0n force applied to a door at a perpendicular distance of 0.25 m from the hinge

You seem to be confusing tongues with torques.
Review the definition of tor 
Torque is force times distance from an axis of rotation (the hinge in this case)
Multiply the two numbers you have been given 
T=(f)(d)
torque=force x distance
T=40NM
D=30cm=0.3m
F=?
T=(f)(d)...F=T/D
F=40NM/0.3m
=133.3N 
0.37