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4/11? (1/2)(4/11) + (1/2)(4/11)

or should I be using P(A) x P(B) for this?

- Thread starter ms. confused
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4/11? (1/2)(4/11) + (1/2)(4/11)

or should I be using P(A) x P(B) for this?

- #2

Silverwing

P(A) = 4/11 (There are 4 red jelly beans for Joan to pick, out of a total possible 11)

P(B) = 3/10 (After Joan has now taken a red jelly bean, obviously there are only 3 left and a total possible 10 to pick)

Your question wants Joan AND Jim to pick a red jelly bean, so you should multiply the two. If the question wanted either Joan OR Jim to pull one, you would add the probabilities.

Not too sure where you got (1/2)(4/11) from :P Maybe if you post your reasoning, we could help you out.

P(B) = 3/10 (After Joan has now taken a red jelly bean, obviously there are only 3 left and a total possible 10 to pick)

Your question wants Joan AND Jim to pick a red jelly bean, so you should multiply the two. If the question wanted either Joan OR Jim to pull one, you would add the probabilities.

Not too sure where you got (1/2)(4/11) from :P Maybe if you post your reasoning, we could help you out.

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As Silverwing has said, they are both taking a bean, which means it is an 'AND' situation. If the question said they replaced it then the two events would be independent but the question suggests they are not independent of each other.ms. confused said:

4/11? (1/2)(4/11) + (1/2)(4/11)

or should I be using P(A) x P(B) for this?

The Bob (2004 ©)

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Pyrrhus

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- #5

HallsofIvy

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On the contrary, this is an example ofCyclovenom said:

That's why Silverwing and The Bob use

Of course, the problem doesn't say that Jim picked before Joan but it doesn't matter- if Joan picks first the probability that she picks a red jellybean is 4/11 and the probability that Jim picks red given that Joan picked red is 3/10 so you get exactly the same answer: (4/11)(3/10)= 6/55.

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