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# In a room filled with 7 people, 4 people have exactly 1 sibling in the

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Intern
Joined: 14 May 2018
Posts: 4
In a room filled with 7 people, 4 people have exactly 1 sibling in the  [#permalink]

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09 Aug 2018, 20:22
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In a room filled with 7 people, 4 people have exactly 1 sibling in the room and 3 people have exactly 2 siblings in the room. If two individuals are selected from the room at random, what is the probability that those two individuals are NOT siblings?

How do I solve this? Having a lot of trouble just wrapping my head around what numbers to even start with here!
Intern
Joined: 16 Jul 2018
Posts: 7
Re: In a room filled with 7 people, 4 people have exactly 1 sibling in the  [#permalink]

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09 Aug 2018, 21:19
I think the only combination is three groups where AA BB CCC satisfies the above criteria. So to select two out of three groups. 2 * 2 + 2 * 3 + 2* 3 = 16

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Posts: 51100
Re: In a room filled with 7 people, 4 people have exactly 1 sibling in the  [#permalink]

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09 Aug 2018, 23:29
mikehaueisen wrote:
In a room filled with 7 people, 4 people have exactly 1 sibling in the room and 3 people have exactly 2 siblings in the room. If two individuals are selected from the room at random, what is the probability that those two individuals are NOT siblings?

How do I solve this? Having a lot of trouble just wrapping my head around what numbers to even start with here!

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Re: In a room filled with 7 people, 4 people have exactly 1 sibling in the &nbs [#permalink] 09 Aug 2018, 23:29
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# In a room filled with 7 people, 4 people have exactly 1 sibling in the

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