What percent of the students at Jefferson High School study French but not Spanish?
(1) 30% of all students at Jefferson High School study French.
(2) 40% of all students at Jefferson High School do not study Spanish.
Let us assume there are 100 students then, we have
Total= No. of students that study French (F) + No. of Students that study (S) - no. of students that study both (B) + Neither (N)
Thus we have
St 1 gives us F only so not sufficient
So, Option A and D ruled out
St 2 ----> F+ N = 40
Alone not sufficient, so B ruled out
Combining we get S-B = 60, We still cannot find out S and B therefore insufficent and hence ans E
During GMAT time under time constraint , if we go by the simple logical question of - no information given about the possibility of a student studying either language , wont this itself give the option 'E'