a question for instructors

[emma]

this is a question from MGMAT CAT:

At Jefferson Elementary School, the number of teachers and students (kindergarten through sixth grade) totals 510. The ratio of students to teachers is 16 to 1. Kindergarten students make up 1/5 of the student population and fifth and sixth graders account for 1/3 of the remainder. Students in first and second grades account for 1/4 of all the students. If there are an equal number of students in the third and fourth grades, then the number of students in third grade is how many greater or fewer than the number of students in kindergarten?
12 greater
17 fewer
28 fewer
36 fewer
44 fewer

This is supposedly a 600-700 level question. Firstly the question lays out 6 relationships before it poses the real question - what is the difference between the number of third grade students and kindergarten students?

Do you feel this question is representative of a real GMAT 600-700 level question. With all the relationships laid out, it is fairly difficult to do this in 2 mins even though the math is relatively simple?

thanks

[jwinawer]

it is unrealistically hard (meaning too much calculation, not too complicated, as you say). it took me 2:45 and i have been teaching gmat for years. don't sweat it.