So a coin has 2 sides. So the chance for landing on head has a 50% for one try. Since we are trying to figure out the probability of getting 7 heads in a row, we do 1/2•1/2•1/2•1/2•1/2•1/2•1/2. So the chance of getting 7 heads in a row will be one out of a hundred and twenty eight or 1/128 of a chance.
