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Probability Math ?

I need help with 78 and 80. 

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1 Answer

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  • Alan
    Lv 7
    2 months ago
    Favorite Answer

    Won't use there notation 

    n_C_k   , I will write as   C(n,k)      

    so both answers are hand feed to you 

    Just do the math  

    C(n,k) (p)^n (1-p)^(n-k)    is the formula for all answers 

    C(n,k) = n! / ( k! (n-k)! )  

    so 

    78.  

    they tell you it gives you 

    C(10,3) (1/4)^3 (3/4)^7   

    C(10,3) = 10! / (3! 7!) = 10*9*8/ 3*2*1  =   10*9*4/3  = 10*3*4  = 120 

    C(10,3) (1/4)^3 (3/4)^7 =  120* ( 3^7/ 4^10)  = 

    = 262440/  1048576   = simplified   32805 / 131072 

    Exact answer   32805 / 131072  

    = approximate 0.250282288  

    80.   

    again , they tell you the answer is  

    C(8, 4) (1/2)^4 (1/2)^4   

    = C(8,4)  (1/2^8) 

    = C(8,4) ( 1/256)  

    C(8,4) = 8!/ (4! 4!) = 8*7*6*5/ 4*3*2*1  

    8/(4*2)  =1    

    6/3*1 = 2 

    C(8,4) =    7*2*5  =   14*5 =  70  

    =C(8,4) (1/256) = 70/256  =  35/ 128  =  

    exactly   35/128   

    approximately =  0.2734375

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