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# Not sure of the answer (Venn Diagrams). watch

1. Howdy . I have attached the question and answers I am working on.

I don't understand part b(ii). I get that P(B U T) is 10 + 8 + 4 + 6 + 11 + 3 = 42 which is the bottom part of the fraction as of the 'given by |' part.

I just don't get why we only use 15 for P(Z)

Wouldn't we take all the Z values for P(Z). 15 + 3 + 4 + 8.

I just don't get how we take 15 for the numerator. Could some please explain?

Thanks
2. (Original post by jojo55)

Howdy . I have attached the question and answers I am working on.

I don't understand part b(ii). I get that P(B U T) is 10 + 8 + 4 + 6 + 11 + 3 = 42 which is the bottom part of the fraction as of the 'given by |' part.

I just don't get why we only use 15 for P(Z)

Wouldn't we take all the Z values for P(Z). 15 + 3 + 4 + 8.

I just don't get how we take 15 for the numerator. Could some please explain?

Thanks
You need to use the rule P(A|B) = P(A n B)/P(B)

Identify which bit of the Venn Diagram gives you P(Z n (B u T)), and which bit gives you P(B u T), then divide

Both probabilities will be out of 70, so you can do some cancelling.

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