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2 distinct vertices of an octagon are chosen at random. What is the probability that they are adjacent?

Lightning  Mar 29, 2018
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 #1
avatar+85759 
+3

The total number of pairs  =  C(8,2)  =  28

Adjacent pairs

(1,8) (1,2) (2, 3) (3,4) (4, 5) (5, 6) (6, 7) (7, 8)

 

So....the probability  is

 

8 / 28    =

 

2 / 7

 

 

cool cool cool

CPhill  Mar 30, 2018
 #2
avatar+2347 
+1

An octagon has 8 vertices, and the question says,  "2 distinct vertices of an octagon are chosen at random. What is the probability that they are adjacent? So, this is just 8C2=28 total pairs. Thus, the answer is 8/28=4/14=2/7 smileysmiley

tertre  Mar 30, 2018

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