The words impossible, unlikely, likely, and sure are fundamental to classify how likely events are. If one introduces several number ones into a bag and picks up a number at random, for sure one will get a one and it is impossible to get a two. If one introduces 9 ones into the bag and only 1 two, then getting a one is likely and getting the two is unlikely. In the number line between zero and one, we have 0 = impossible < unlikely < likely < sure = 1. Picking up numbers at random from the bag means picking up without peeking into the bag! If half of the numbers if the bag are ones and the other half are twos, then picking up a one and a two are equally likely. Equally likely sits between unlikely and likely in the number line.
We can also understand Impossible, unlikely, likely, and sure using spinners. In the example below, we “open up” a spinner with six sectors and map it into the number line. Therefore, fractions can also be used to indicate how likely events are. For example, 1/6 and 2/6 map into unlikely events, whereas 4/6 and 5/6 map into likely events.