Observe first 5 consecutive 0 s Summation rule: the first 5 consecutive 0 's could start at position , or 6 Start at the first position Other 5 bits can be anything: Start at the second position The first bit must be a 1 There are various possibilities that can be included in it. Remaining bits can be anything: Start at third position The second bit must be a 1 due to above-mentioned reason. First bit and last 3 bits can be anything: Starting at 4,5 and 6 positions Same as starting at positions 2 or each Total The five consecutive 1's ensue the same pattern and have different like 112 possibilities There would be two cases counted twice (that we thus need to exclude): 0000011111 and 1111100000 Total