the probability of getting heads on a two-face coin is simply 1/2.
now, what is the probability of getting 1/2 AND 1/2 AND 1/2 AND 1/2 AND 1/2? well, AND means "times", namely
well, and since it's a two-face coin, the probability for each face is equal, 1/2, so Heads has a chance of 1/2 each time, or we can also say that Tails has a chance of 1/2 each time, so if Tails has the same probability over 5 times as Head does.