If a fair coin is tossed once, the probability of getting a HEAD is
A$0$
B$1$
C$1/4$
D$1/2$
Answer & Solution
Correct answer: D. $1/2$
1. For a fair coin, the sample space is $S = \{H, T\}$ with each outcome equally likely.
2. Probability of an event $E$ for equally-likely outcomes: $P(E) = \dfrac{|E|}{|S|}$.
3. Here $E = \{H\}$, $|E| = 1$, $|S| = 2$. So $P(E) = 1/2$.
4. Probabilities always lie in $[0, 1]$: option A (0) means impossible event; option C (1) means certain event.
5. Option D ($1/4$) would correspond to TWO coin tosses both being heads, not one.
_Source: NCERT Class 11 Mathematics, Ch 14, §14.2.2 (Probability of equally likely outcomes), p. 7._
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