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?
let number of boys in a class are x
then number of gals become 36-x
x cannot be 36 as there are some gals in class
so maximum value of x/12 can be 2
any other method to solve this question.
Lets apply process of elimination
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.