Measuring the likelihood of an event
Probability is a measure of how likely an event will occur; a flipped coin has a 50% (or 1/2) probability of landing with its head up. In these exercises, students determine the probability of events by counting the number of ways an event can happen (the numerator) divided by the total number of possible outcomes. Note that this method only works if each different outcome is equally likely to happen at any time.
Source: k5learning