ratios question

[luckystrike31415]

problem is from a sample CAT exams. i'm looking for solutions UNDER 2 min! good luck!



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?

a 12 greater
b 17 fewer
c 28 fewer
d 36 fewer
e 44 fewer

[kartikeya.payautomata]

Ok a simple question took me 1 min 20 secs as i am slow in calculations .

Solution

Ratio of teachers to students is given =1:16.
So number of students = (16/17)*510=480.

As per data table is given below
No of students in
1)kinder = 96
2)1st G + 2nd G=120
3)3rd G+4th G= 2x.
4)5th G+ 6th G= 128.

so adding all we have 2x=136.
so x=68.
So difrrence in k and 3rd grade = 96-68
=28 fewer

[tim]

Not much to this one, after you recognize that there are 30 teachers. Everything else is just a straightforward calculation you should be able to do fairly quickly..