The probability of guessing correctly at least 8 out of 10 answers on a true-false type examination is


In the examination , we have only two option True and False.

So, The probability of getting True is , p= 1/2


And, similarly, probability of getting False is, q=1/2


The total number of Answer in examination , n=10


The probability of guessing correctly at least 8 it means r=8,9,10


We know, probability distribution P(X=r)=nCr (p)r qn-r


P(X=r)=P(r=8)+P(r=9)+P(r=10)


= 10C810C9 10C10



[45+10+1]



[


Hence, Probability is

85
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