[Cap&Ball]

It's an illusion:

[csense]

So as along as the lines are a couple miles apart, the graph makes sense?

[Cboldt]

-- It's an illusion ... --

The illustration shows "projecting" fractions onto a common line (the top line).

The technique works, regardless of where, vertically, the segmented/fraction lines are drawn.

Some kids might have the light go on, seeing this, but most won't.