Discussion
2 fair coins are tossed. What is the probability of getting exactly 2 heads or 2 tails ?
Answer: C
The probability is \(\frac{1}{2}\).
Two fair coins give four equally likely outcomes: HH, HT, TH and TT. Exactly 2 heads is HH, and exactly 2 tails is TT; the two events cannot happen together, so their probabilities add:
\[ P = \frac{1}{4} + \frac{1}{4} = \frac{1}{2} \]
\(\frac{1}{4}\) is the probability of only one of the two events, for example just HH. \(\frac{1}{3}\) comes from wrongly treating HH, TT and 'one of each' as equally likely, and \(\frac{3}{8}\) belongs to a three-coin question.
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