+0  
 
 #1
avatar+111455 
+1

P( no fives)  =  (5/6)^9

P( 1 five)  = C(9,1)(1/6)(/6)^8

P(2 fives) = C(9,2) ( 1/6)^2 ( 5/6)^7

P(3 fives) =  C(9,3) (1/6)^3(5/6)^6

P(4 fives) = C(9,4)(1/6)^(4)(5/6)^5

 

So....the probability is just the sum of these

 

(5/6)^9 + C(9,1)(1/6)(5/6)^8   + C(9,2)(1/6)^2 (5/6)^7 + C(9, 3)(1/6)^3(5/6)^6 + C(9, 4) (1/6)^4 (5/6)^5

 

≈ .99   ≈  99%

 

 

cool  cool   cool

 Apr 11, 2019

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