### Video Transcript

Chuck’s football and his Frisbee
are stuck in a tree. Chuck shakes the tree until both
items fall out. The probability that the football
falls out of the tree first is three-quarters. What is the probability that the
Frisbee falls out of the tree first?

The events in this question are an
example of what’s known as complementary events. This means that these events cover
all possibilities. Either the football falls out of
the tree first or the Frisbee falls out first. There are no other
possibilities.

A key fact about complementary
events is that the sum of their probabilities is always equal to one. For this question, this means that
the probability that the football falls out of the tree first plus the probability
that the Frisbee falls out of the tree first is equal to one.

We’re told in the question that the
probability that the football falls out of the tree first is three-quarters, so we
can substitute this value into our equation. Now we just need to solve this
equation to find the probability that the Frisbee falls out of the tree first.

It’s a relatively straightforward
equation to solve. We just need to subtract
three-quarters from each side of the equation, giving the probability that the
Frisbee falls out of the tree first is equal to one minus three-quarters. There are four-quarters in one
whole, so one minus three-quarters is equal to one-quarter. The probability that the Frisbee
falls out of the tree first is one-quarter.