What is the probability of flipping two coins and both landing on heads

The probability of getting heads on the toss of a coin is 0.5. If we consider all possible outcomes of the toss of two coins as shown, there is only one outcome of the four in which both coins have come up heads, so the probability of getting heads on both coins is 0.25. The second useful rule is the Sum Rule.

Probability is 0.5% ...