GMATD11 wrote:

In a certain class consisting of 36 students, some boys and some girls, exactly 1/3 of the boys and exactly 1/4 of the girls walk to school. What is the greatest possible number of students in this class who walk to school?

A. 9

B. 10

C. 11

D. 12

E. 13

let number of boys in a class are x

then number of gals become 36-x

1/3x+1/4(36-x)=9+x/12

x cannot be 36 as there are some gals in class

so maximum value of x/12 can be 2

Answer C

any other method to solve this question.

Lets apply process of elimination

option A:

See, 9 cannot be expressed as sum of multiple of 3 and 4.

neither can 10, 12 or 13.

only 11 can be expressed a sum of multiples of 3 and 4.

11= 3+ 2(4)

since we need 1/3 of boys, 1/4th of girls. and number of boys and girls have to be integers.

11 is the only option that satisfies the situation.