CAT Quant question

[shahlageoffrey]

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?

5/21
3/7
4/7
5/7
16/21

Please explain how can I solve for this question.

Thanks

[jnelson0612]

Please read through this thread and let us know if you have further questions: siblings-problem-combinatorics-t9048.html?hilit=In%20a%20room%20filled%20with%207%20people

[nhatha_dn]

jnelson0612, Can you please post the link again? Thanks.

[RonPurewal]

siblings-problem-combinatorics-t9048.html

That's a really long and exhaustive thread, so I'm going to lock this one (and delete it soon enough).