Question

The coin is tossed m times. Find the probability p that the head appears at least k times and at most l times

Answer 1

There are 2^m possible results. $C^k_m$ is the number of results with k heads. Probability of k heads is $\frac{C^k_m}{2^m}$ .

So probability from k till l heads is

$P=\sum^l_{i=k}\frac{C^i_m}{2^m}$