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Edexcel s1

http://pmt.physicsandmathstutor.com/download/Maths/A-level/S1/Papers-Edexcel-Tiered/09%20Gold%201%20-%20S1%20Edexcel.pdf

Question 7)g) is what i'm stuck on. I was writing out all the possible combinations but I went wrong somewhere. Does anybody know any quicker methods to work this out?

Reply 1

ThomH97

You will need to work out the possible combinations and their probabilities, yes. Have you doubled some of the probabilities such as S1=1, S2 = 2 to get S1=2, S2 = 1?

Reply 2

emx_eco

Original post by ThomH97

You will need to work out the possible combinations and their probabilities, yes. Have you doubled some of the probabilities such as S1=1, S2 = 2 to get S1=2, S2 = 1?

Yeah, I did that. I got 0.64 but the mark scheme said the answer was 0.57 :s-smilie:

Reply 3

ThomH97

Possibly you've added extras in if you've gone too high? (I agree with 0.57 btw)

I did it by following their part (f), for all the possible values of S1. So if S1 = 0 means S2 can have all the other values so 0.2 x 1, S1 = 2 means S2 can be 0, 1, 2 so 0.1 x 0.5 and so on. What probabilities have you got?