When tossing a coin, there are two possible outcomes: heads or tails.
The sample space is all possible outcomes that can happen. So the sample space of this problem is:
In order to write the probability of a head appearing, we have the following fraction:
Numerator: number of times the event occurs in the sample space. "Heads" appears 1 time in the sample space, so the numerator of the probability fraction is 1.
Denominator: number of elements in the sample space. There are two elements in the sample space: heads and tails.
Therefore, the probability of the event "a head appears in a single toss of a coin" is given by: