Complementary events in probability are two outcomes that include every possible result of a situation.

Let's think about a basketball game.

When a team plays, there are two main outcomes: they can either win or lose.

We can write the chances of these events like this:

• The chance of the team winning is called $P(W)$.
• The chance of the team losing is called $P(L)$.

These two probabilities add up to 1:

$P(W) + P(L) = 1$

Example:

Imagine a basketball team has a 70% chance of winning.

We can show this like this:

• $P(W) = 0.7$ (which means a 70% chance of winning)
• $P(L) = 1 - P(W) = 0.3$ (this means a 30% chance of losing)

By understanding complementary events, teams can make better choices based on how likely they are to win or lose.