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# s1: probability stuck on question watch

1. Hi, I'm not struggling with a question from my textbook, the answer is P(B=0.5 which works but I don't know how to get it

The only way I could think about doing it would be trial and error which obviously isn't going to get me a good answer!

I was thinking you could do 0.6xP(B) + 0.4xP(B) + 0.6xP(B') =0.7 but that wouldn't work would it as how can we assume P(B)=P(B')?
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2. (Original post by Jitesh)
Hi, I'm not struggling with a question from my textbook, the answer is P(B=0.5 which works but I don't know how to get it

The only way I could think about doing it would be trial and error which obviously isn't going to get me a good answer!

I was thinking you could do 0.6xP(B) + 0.4xP(B) + 0.6xP(B') =0.7 but that wouldn't work would it as how can we assume P(B)=P(B')?
I'm assuming this is Q12:

Use the formula :

Usually written with symbols :

Also, since A and B are independent you have the formula

3. (Original post by notnek)
I'm assuming this is Q12:

Use the formula :

Usually written with symbols :

Also, since A and B are independent you have the formula

Sorry I meant q11, but it seeems like you answered q11?

Sorry what does the cup mean? and/or ?
4. (Original post by Jitesh)
Sorry I meant q11, but it seeems like you answered q11?

Sorry what does the cup mean? and/or ?
Yes I meant Q11

5. (Original post by notnek)
Yes I meant Q11

Sorry I'm confused on to how you would get P(AnB) without knowing the value of B?
6. (Original post by Jitesh)
Sorry I'm confused on to how you would get P(AnB) without knowing the value of B?
If you combine the first formula with the second formula I gave you:

You know and so you can work out .
7. (Original post by notnek)
If you combine the first formula with the second formula I gave you:

You know and so you can work out .
Oh, that's great! Thank you very much!

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Updated: February 5, 2016
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