Starter
Draw a number line and work out the following:
1. What is a fraction that is between one half and one
third?
2. What is a fraction that is between two fifths and
one quarter?
3. What is a fraction that is between two thirds and 4
fifths?
0
½
1
LI: To understand Probability and
Chance
SC: Calculate Probabilities
Probability

Probability is a measure of how likely it is
for an event to happen.
 We name a probability with a number from
0 to 1.
 If an event is certain to happen, then the
probability of the event is 1.
 If an event is certain not to happen, then the
probability of the event is 0.
Probability

If it is uncertain whether or not an event
will happen, then its probability is some
fraction between 0 and 1 (or a fraction
converted to a decimal number).
B A
C D
3
1
2
A
C B
1. What is the probability that the spinner
will stop on part A?
2. What is the probability that the
spinner will stop on
(a) An even number?
(b) An odd number?
3. What fraction names the
probability that the spinner will
stop in the area marked A?
Probability Activity

Obtain a handful of glass pebbles.
 Put ten of one colour (white) and five of
another colour (black) in a container.
 Ask your group, what is the probability of
getting a white one?
 Ask your group, what is the probability of
getting a black pebble?

Another person in the group will then put in
8 white pebbles and 2 black ones in.
 Ask the group to predict which color you
are more likely to pull out, least likely,
unlikely, or equally likely to pull out.
 The last person in the group will make up
his/her own problem with the glass pebbles.
Probability Questions

Lawrence is the captain of his track team.
The team is deciding on a color and all eight
members wrote their choice down on equal
size cards. If Lawrence picks one card at
random, what is the probability that he will
pick blue?
blue
blue
yellow
red
green
black
blue
black

A.
B.
C.
Donald is rolling a number cube labeled 1
to 6. Which of the following is LEAST
LIKELY?
an even number
an odd number
a number greater than 5
CHANCE

Chance is how likely it is that something
will happen. To state a chance, we use a
percent.
½
0
Certain not
to happen
0%
Probability
Equally likely
to happen or
not to happen
Chance
50 %
1
Certain to
happen
100%
Chance

When a meteorologist states that the chance
of rain is 50%, the meteorologist is saying
that it is equally likely to rain or not to rain.
If the chance of rain rises to 80%, it is more
likely to rain. If the chance drops to 20%,
then it may rain, but it probably will not
rain.
1 2
4 3
1. What is the chance of spinning a
number greater than 1?
4 1
2
3
5
2. What is the chance of spinning a
4?
3. What is the chance that the
spinner will stop on an odd
number?
4. What is the chance of rolling an even
number with one toss of on number cube?
Probabilities when Outcomes
are Equally Likely
Math Message
Which phrase –
Extremely likely
 50-50 chance, or
 Very Unlikely

best describes the chance of picking a red
card from a regular deck of playing
cards?
Words we use to describe the
likelihood of events
Impossible
Extremely unlikely
Very unlikely
Unlikely
50-50 or even chance
Likely
Very likely
Extremely likely
Certain
Comparing Two Events
Picking a heart is _____________ than picking
the 9 of hearts.
More likely
Equally likely
Less likely
Comparing Two Events
Picking a red card and picking a black card are
____________.

More likely

Equally likely

Less likely
Comparing Two Events
Picking a face card is _______ than picking a
non-face card.

More likely

Equally likely

Less likely
Finding the Probability of
Events
When you randomly draw a single card from a
deck of cards, 52 equally likely results or
OUTCOMES are possible.
An event is the specific set or collection of
possible outcomes in which you are
interested.
Probability is the number from 0 to 1 that tells
the chance that an event is going to happen.
Formula
Probability of an event = number of favorable outcomes
number of possible outcomes
A favorable outcome is an outcome that meets the
conditions of an event that will make the event happen.
Picking a heart is an event. A favorable outcome is picking a
2, 3, 4, 5, 6, 7, 8, 9, 10, J, Q, K, or A of hearts. There are 13
favorable outcomes out of 52 possible outcomes.
The probability of the event is = 13
52
Practice
Probability of an event = number of favorable outcomes
number of possible outcomes
Picking a face card is an event.
A favorable outcome is picking a J, Q, or K of hearts,
diamonds, spades, or clubs.
How many favorable outcomes are there? ____
How many possible outcomes are there?
So the probability is
____
____
Brainpop

BrainPOP | Basic Probability