Question #ba1dc

1 Answer
Jun 5, 2015

There are four possible sequences of flips. Each is equally likely.

  • Heads, Heads
  • Heads, Tails
  • Tails, Heads
  • Tails, Tails

Since since the combination of tails twice in a row is one of four, you can calculate the probability as #1/4#.

This can also be done by multiplying the probability of a particular outcome by the probability for each trial. You know that the probability of tails for each trial is #1/2#. You can calculate the probability for two tails in a row as:
#1/2 * 1/2 = 1/4#