Posted by Carline on Thursday, March 19, 2009 at 11:19am.
Of 120 students, 60 are studying French, 50 are studying Latin and 20 are studying French and Latin. Find the probability that a student is: (a) studying French or Latin and (b) studying neither.

Statistics/probability  PsyDAG, Thursday, March 19, 2009 at 11:27am
Assuming that the 60 and 50 are studying only one language, there cannot be 20 studying both out of 120 students. Do you have your total number of students wrong?
Repost with correct data. Thanks for asking. 
Statistics/probability  Reiny, Thursday, March 19, 2009 at 11:41am
P(F or L) =P(F) + P(L)  P(F and L)
= 60/120 + 50/120  20/120
= 90/120
= 3/4
or you could make Venn diagrams showing overlapping circles for French and Latin within a universal set of 120
enter 20 in the intersection of the two circles.
then 40 would go in the nonoverlapping part of French and 30 in the nonoverlapping part of Latin
total of inside of both circles = 40+20+30 = 90
So Prob of F or L is 90/120 = 3/4
for b) number of students outside the two circles is 12090 = 30
so Prob of neither F or L is 30/120 = 1/4