If you toss a coin 7 times what is the probability of gettin

If you toss a coin 7 times what is the probability of getting exactly 2 heads?

Solution

Note that the probability of x successes out of n trials is          
          
P(n, x) = nCx p^x (1 - p)^(n - x)          
          
where          
          
n = number of trials =    7      
p = the probability of a success =    0.5      
x = the number of successes =    2      
          
Thus, the probability is          
          
P (    2   ) =    0.1640625 [ANSWER]