[maxerickson]

I see that question as being useful because it assesses several different understandings at the same time; the key ones I see are the understanding of fractions (including the idea of improper fractions) and the ordering of the values represented.

A human instructor asks for the explanation to explore a bit if the answer was just a guess or if it was reasoned out, and whether the reasoning was correct. An automated evaluation system would have an easier time factoring in results from previous evaluations (it can perfectly remember an arbitrary number of tests across an arbitrary number of students...) and could check understanding by presenting several questions (it won't get sick of looking at the answers).

I guess if the proposition is that human instruction can be replaced by automated systems that is crazy. Really, I expect most people are looking to supplement it and to make it more effective.