Data Sufficiency

In a certain senior class,72 percent of the male students and 80 percent of the female students have aplied to college.What fraction of the students in the senior class are male?

1.There are 840 students in the senior class.
2.75 percent of the students in the senior class have applied to college.

IMO C

1) talks about the total number of students in the class.
It doesn't lead to any concrete solution.

2) gives the % of students as a whole.
Assuming the total number of male students to be x and total number of students to be y, we can arrive at the following equation:

72% of x + 80% of (y-x) = 75% of y
This doesn't provide a concrete solution either.

Combining both, we have

72% of x + 80% of (840-x) = 75% of 840

On solving this we get x = 525.

Hence % of males in the class is 525/840*100.

Hence IMO C

but the answer is B according to GMAT prep

Sorry mate,

My bad. Just realized my mistake.

Assume men = x and women = y.

Hence,
72% of x + 80% of y = 75 % of (x+y)

=> 72x + 80y = 75x + 75y

=> x/y = 5/3

=> x/(x+y) = 5/8.

Hence, B is the answer.

And apologies for giving the wrong explanation earlier