> Why not? Did they thing the actual answer was smaller or larger?

Good question - I don't know. I didn't pursue it, but where it was obvious, smaller. Thinking back now, years later, my impression of one student, is that of a feeling of great smallness, contrasted with a concrete length, maybe yielding a "no, that doesn't feel small enough".

> Is the answer not yellowish-white?

What color is sunlight? ;)