Question 355048

probability of getting head= 1/2

probability of getting tail = 1/2


Using binomial probability


Probability of getting the 0 heads =10C0 * (1/2)^0 * (1/2)^10 = (1/2)^10



Probability of getting the 1 heads =10C1 * (1/2)^1 * (1/2)^9 = 10 *(1/2)^10



Probability of getting the  2 heads =10C2 * (1/2)^2 * (1/2)^8 = 45 * (1/2)^10


now, 
probability of getting at most 2 heads = 56 * (1/2)^10 
                              (after adding above 3 value)


ans =  7/128


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