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# X is necessary for Y to happen Z is sufficient for Y to

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Intern
Joined: 03 Aug 2004
Posts: 46
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X is necessary for Y to happen Z is sufficient for Y to [#permalink]

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24 Nov 2004, 23:40
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X is necessary for Y to happen

Z is sufficient for Y to happen

Can we conclude
1-- If Y happens X happened
2-- IF Y did not happen X did not happen
3-- If Y happened Z happened
4-- If Y did not happen, Z did not happen

Could someone explain ?
Senior Manager
Joined: 19 Oct 2004
Posts: 317
Location: Missouri, USA
Followers: 1

Kudos [?]: 66 [0], given: 0

Re: CR necessary and sufficient [#permalink]

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25 Nov 2004, 01:28
taklu wrote:
X is necessary for Y to happen

Z is sufficient for Y to happen

Can we conclude
1-- If Y happens X happened
2-- IF Y did not happen X did not happen
3-- If Y happened Z happened
4-- If Y did not happen, Z did not happen

Could someone explain ?

I think its 1. Since X has to happen for Y to happen, we can say tha if Y happens, then X happened.

2--- it might be that X happened, but Y didnt happen. Its not said that if X happens, then Y has to happen.

3-- Its not mentioned that if Z happened, then Y also happened. Instead it given that X must happen for Y to happen.

4.. it might be that Z happened, but Y did not.

Not very sure though..
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Manager
Joined: 15 Jul 2004
Posts: 75
Location: London
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25 Nov 2004, 02:08
I think it is 1 too.

1- True, Since X is necessary for Y, if Y happened it is because X happened before.

2- It doesnâ€™t say that if X happens, then Y will necessarily happens. Y can happen or not when X happens.

3- If Y happens, Z could have happened or not. Z is not a condition.

4- Similar to statement 2: if Y does not happen, Z could have happed or not.
Director
Joined: 07 Nov 2004
Posts: 689
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Re: CR necessary and sufficient [#permalink]

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25 Nov 2004, 08:23
taklu wrote:
X is necessary for Y to happen

Z is sufficient for Y to happen

Can we conclude
1-- If Y happens X happened
2-- IF Y did not happen X did not happen
3-- If Y happened Z happened
4-- If Y did not happen, Z did not happen

Could someone explain ?

I will pick 1 too. But I have a problem with the question stem... If Z is sufficient for Y to happen it implies that just Z is enough for Y to happen then how can X be necessary for Y to happen?
Senior Manager
Joined: 19 Oct 2004
Posts: 317
Location: Missouri, USA
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Re: CR necessary and sufficient [#permalink]

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25 Nov 2004, 13:32
gayathri wrote:
taklu wrote:
X is necessary for Y to happen

Z is sufficient for Y to happen

Can we conclude
1-- If Y happens X happened
2-- IF Y did not happen X did not happen
3-- If Y happened Z happened
4-- If Y did not happen, Z did not happen

Could someone explain ?

I will pick 1 too. But I have a problem with the question stem... If Z is sufficient for Y to happen it implies that just Z is enough for Y to happen then how can X be necessary for Y to happen?

Well Z maybe enough, but X is NECESSARY. Suppose, I can leave my home when my mom returns, but i need to tell her something very imp. before leaving. So it is NECESSARY that she come \s back before I leave. My dad might come back in the middle (which is sufficient for me to leave), but it is not NECESSARY. So I cant leave even when he comes back.. am I making my point clear?
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Manager
Joined: 11 May 2004
Posts: 67
Location: Michigan
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25 Nov 2004, 18:12
My guess is that this is not a question itself.
Taklu is trying to get his concepts clear. Good discussion though
I agree 1 must be true.
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