Page 430 - Math Smart - 7

The favourable outcome is rolling a 5 on each die.

Probability of rolling a 5 on a 5-sided die = number of favourable outcomes
total number of possible outcomes
= ^ or 0.167 or 16.7%

number of favourable outcomes
Probability of rolling an 8 on an 8-sided die =
total number of possible outcomes
= ^ or 0.125 or 12.5%

The probability of June rolling a 5 on a 6-sided die is higher than rolling a 5 on an
8-sided die. This means that June is more likely to roll a 5 on a 6-sided die than on
an 8-sided die.
It is useful to use a probability tree diagram in situations where the number of
possible outcomes is not clear.

A 4-slded die shows the
numbers 1 to 4.
I
Why do we say that this
die has rolled a 4?
Discuss with a partner.
Tim rolls a 4-sided die.
a) Draw a probability tree diagram to show all the possible outcomes.
b) List the possible outcomes.
c) Calculate the probability of Tim rolling:
I) a 4, ii) an even number and iii) a zero.
A bag contains 4 yellow balls, 3 blue balls and 1 pink ball. One ball is
selected.
a) Draw a probability tree diagram to represent the sample space.
b) List all the possible outcomes.
c) Calculate the probability of selecting a yellow ball.

Anni, Kati, Patty and Lee are going to the movies. There is only one ticket
left for the movie that they all want to watch. They decide to write each
of their names on a separate piece of paper to randomly choose who will
watch the movie.
a) Draw a probability tree diagram to show all the possible outcomes in
the sample space.
b) What is the probability that Lee will watch the movie?
c) If Patty decides to give her movie ticket to Lee if her name is selected,
what is the probability of Lee watching the movie?
d) If Patty decides not to enter her name in the draw, what is the
probability of Lee watching the movie?
e) Compare your answers in parts (b), (c) and (d). Under what
circumstances does Lee have the best chance of watching the movie?

^26 UNIT 18 Probability