This ratio will be true for any square so for simplicity let A = (0,0) B=(0,1) C=(1,1) D=(1,0) M=(.5,1) Midpoint AM=(.25,.5) Slope AM=2 The crease is the perpendicular bisector of AM y-.5=-.5(x-.25) y=-.5x+6.25 X=(0,.625) AX=.625 If x=1, y=.125 Y=(1,.125) DY=.125 AX/DY=.625/.125=5