Originally Posted by ohmathmom
I really don't know what the MAA means by top 40%; that's the percentage given by them in the Achievement Role description.
http://www.maa.org/math-competitions/about-amc/faq
Looking at the stats, it looks like 12% of students grade six and below make the achievement role.

I see. It says, "AMC 8 Achievement Roll Certificate — given to all students in 6th grade and below who score in (approximately) the top 40%. 15 points or more." Since much less than 40% of contestants (in any grade) get those scores, I suppose they must mean that the (length of the) interval [15,25] is 40% of the (length of the) interval [0,25].