sunland
What fraction of this year's graduating students at a certain college are males?
(1) Of this year's graduating students, 33 percent of the males and 20 percent of the females transferred from another college.
(2) Of this year's graduating students, 25 percent transferred from another college.
Each statement, taken one at a time, is not sufficient.
Taking both statements together:
Let total number of students be t.
Out of these t students, m are male and f are female.
t = m + f
If 25% of total graduating students are transferred then 75% of total graduating students are already present.
Thus, existing students = 0.75 t
transferred students = 0.25 t
If 33% of total graduating male students are transferred then 67% of total graduating male students are already present.
Thus, existing male students = 0.67 m
transferred male students = 0.33 m
If 20% of total graduating female students are transferred then 80% of total graduating female students are already present.
Thus, existing female students = 0.8 f
transferred female students = 0.2 f
Approach 1: If we consider existing students:Total existing students = total existing male students + total existing female students
0.75 t = 0.67 m + 0.8 f
0.75 (m+f) = 0.67 m + 0.8 f (Substituting t as m+f)
0.75 m + 0.75 f = 0.67 m +0.8 f
0.75 m - 0.67 m = 0.8 f -0.75 f
0.08 m = 0.05 f
m/f = 5/8
Approach 2: Alternatively, if we consider transferred studentsTotal transferred students = total transferred male students + total transferred female students
0.25t = 0.33m + 0.2f
0.25 (m+f) = 0.33m + 0.2f (Substituting t as m+f)
0.25 m + 0.25 f = 0.33m +0.2f
0.25 f - 0.2 f = 0.33m - 0.25 m
0.05 f = 0.08 m
m/f = 5/8
Ratio of male to female is same in both approaches i.e. m/f = 5/8Fraction of graduating students who are male = m / t
m/(m+f)= 5/13 (Substituting t as m+f)
Hence, both statements together are sufficient.
C is the correct answer.