When you flip a coin twice, you have a 50/50 chance of it land on heads or tails.
The possible combinations for fliping a coin twice: HH (heads/heads both times) T/H(Tails/Heads) H/T(Heads/Tails) or the one you're looking for... T/T (Tails/Tails both times)
You have a 1/4 chance of getting tails both times.
