geometry
posted by Audrey .
At rosemead high school, 94 students take biology, 86 take ethnic studies, and 95 take geometry. thirtyseven students take both biology and geometry, 43 take geometry and ethnic studies, and 42 take ethnic studies and biology. twenty eight students take all three subjects. What is the probability that a student chosen at random will be taking all three of the courses?

Number(AorBorC)= Number(A) + Number(B) + Number(C)  Number(AandB)  Number(AandC)  Number (BandC) + Number(AandBandC)
= 94 + 86 + 95  37  43  42 + 8
= 161
Prob of (as stated) = 8/161
You could also find the total by using Venn diagrams