Page 426 - Math Smart - 7

CHAPTER 18.2
In this chapter

Pupils should be able to:
• Identify all the possible
mutually exclusive
outcomes of a single
event

Calculating probability

Outcomes which give an event that you are Interested
In are called favourable outcomes for that event.
Remember that In the spinner example earlier, there
are 5 possible outcomes. If you want to know the
probability of the pointer landing on green, then
green is the favourable outcome.
The probability of the pointer landing on green
Is 1 out of 5.
We can also express the
probability as a decimal Only 1 segment satisfies the favourable
and a percentage. This can also be written as 5. outcome green.

1=0.2 There are 5 possible outcomes.
^ X 100% = 20%
To calculate the probability of the favourable outcome, we divided the number of
favourable outcomes by the total number of possible outcomes.

Probability of a favourable outcome = '^^"^ber of favourable outcomes
total number of possible outcomes

Calculate the probability of
a) rolling a 3,
b) rolling an even number,
c) rolling a number less than 6,
d) rolling a number greater than 6 and
e) rolling a number less than 10.
on a die.

Solution
a) Probability of rolling a 3
There Is one 3 on the die.
_ number of favourable outcomes
total number of possible outcomes
There are 6 possible outcomes:
1
- 6 1, 2, 3, 4, 5 and 6.

if*
422 UNIT 18!, Probability
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