SOLUTION: From a group of 100 students, 30 are taking math, 20 are taking chemistry, and of those totals 10 are taking both math and chemistry.What is the probability that a randomly selecte

Question 277508: From a group of 100 students, 30 are taking math, 20 are taking chemistry, and of those totals 10 are taking both math and chemistry.What is the probability that a randomly selected student is taking math or chemistry?
Found 2 solutions by CharlesG2, yuckypants:
Answer by CharlesG2(834) (Show Source): You can put this solution on YOUR website!
From a group of 100 students, 30 are taking math, 20 are taking chemistry, and of those totals 10 are taking both math and chemistry.What is the probability that a randomly selected student is taking math or chemistry?
my guess is the set of Math plus the set of Chemistry equals 50 students, the 2 sets intersect with 10 in each group, leaving 10 in the not interected portion of Chemistry and 20 in the not intersected portion of Math, that is a total of 30 in the not intersected portions of each group
(I drew 2 circles that intersected, one for Math and one for Chemistry.)
if I am right then 30/100 or 30% are taking Math or Chemistry and not both.
please let me know if I am wrong or if you have a better way of figuring this out

Answer by yuckypants(1) (Show Source): You can put this solution on YOUR website!
Sorry, Charles, but that answer is incorrect. You subtracted 10 from each group, totaling 20. You need to subtract 5 from each group. Either way though, it doesn't matter. This is a mutually exclusive problem.
I think this is pretty straightforward - 30 take math, 20 take chemistry, and 10 overlap. The question specifically states "....randomly selected student taking math OR chemistry?"
40%.
30(M)+ 20(C)-10(M&C)=40/100

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