Word Translation problem from Manhattangmat prep exam

[zguest]

I was having problems with efficient guessing strategy and identifying the traps in the answer choices in the question below. Can somebody help out. Thanks

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

[Pathik]

What was your thought process in "efficient guessing strategy"

Pathik

[d]

I don't have any strategy on guessing for this one. I think one of the traps is that "5th graders account for 1/3 of the remainder. When doing these problems I tend to overlook the wording and miss things like that.

I got 28, hopefully that is the right answer, if not, I overlooked a trap. I think on this one you just have to do the math.[/u]

[Vaibhav]

Total Number of Students = 510/17 * 16 = 480

KG student = 480/5 = 96

Remaining Students = 480 - 96 = 384

Students in 5+6 = 1\3 * 384 = 128

Students 1+2 = 480 * 1\4 = 120

Remaining Students = 480 - (96+128+120) = 136

Students 3 = Students 4 = 136/2 = 68

KG - Stud in3 = 96 - 68 = 28

[RonPurewal]

did you take a look at this thread?
http://www.manhattangmat.com/forums/post10744.html

since this problem is more or less pure arithmetic, it's hard to articulate any coherent 'guessing strategy' for it; you just have to dive into the calculations.

none of the calculations is particularly difficult; there are just a lot of them. so, as i said in the other thread, you need to make sure you're ok going without a calculator. if you use a calculator in your everyday life, start going without one every so often just to get back into the groove.