Vector proofs - medians of a triangle are concurrent

[NE2000]

How would you go about this efficiently? There's a thread where a very long solution was posted up (and I can't see it for some reason) but I was hoping for something simpler

The way I was looking at it was triangle OAB and let M be intersection of two medians and N be intersection of two other medians and then prove that OM = ON (vectors; didn't draw the arrows) but I just can't see the solution.

The reason I ask is its on the study design as an example of a vector proof

[/0]

There is a vector proof of it in Chapter 2.5 of Essentials