Video Transcript
A box contains seven white balls,
three black balls, and eight red balls. What is the probability that a ball
drawn at random is black?
We’re told that the ball is drawn
at random, which means every ball has an equal chance of being chosen. When all outcomes in an experiment
are equally likely, we can calculate the probability of a particular event occurring
by dividing the number of successful outcomes by the total number of outcomes. In this case, in which we want to
calculate the probability that the ball drawn is black, the successful outcomes are
all the black balls in the box. The total number of outcomes is the
total number of balls in the box.
The number of black balls is given
in the question; it’s three. The total number of balls in the
box is the sum of the number of balls of each color: seven plus three plus eight,
which is 18. So, the probability that the ball
drawn is black is three out of 18. We can simplify this fraction by
dividing both the numerator and denominator by three. And so we find that the probability
that the selected ball is black is one-sixth.