PROBABILITY question from topscore

[birdman12345]

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Question: What is the probability of 6 tails on 9 tosses of a fair coin?

Answer: 21/128

HOW DO YOU GET THIS ANSWER????????????

 

[checkamundo]

Question: What is the probability of 6 tails on 9 tosses of a fair coin?

Answer: 21/128

HOW DO YOU GET THIS ANSWER????????????

You have to use this eqn:

N!/M!(N-M)! x P^M x (1-P)^(N-M) where M= # of successes in N trials
and P= probability of occurance

So for your problem, the probability of throwing heads or tails = P= 1/2

9!/6!(9-6)! x (1/2)^6 x (1-1/2)^(9-6)