I only had 5 correct even though I knew about the involved bias from several sources and had done the (more extensive) test on http://www.projectionpoint.com/test1.php some time ago.

My main problem was the sheer scale of some problems, like the volume of the Great Lakes, which screwed up all the calculations in my head. Also, I did actually kinda-know a few of these items, but misremembered them and overconfidently didn't adjust my margins for safety.

Still, hitting a target with over 10 orders of magnitude in range isn't exactly accuracy.