1.
Grade 9 | Unit 9.3 | Page 12
Unit 9.3
Learning Activity 9.3 with Answers
WHAT ARE MY CHANCES?
Names:
Calculate the probabilities of the following. Circle the correct answer.
Remember:
Probability = number of favourable outcomes
total number of possible outcomes
Activity 1 - dice throwing
1. You bet that the die will land on a number higher than 4. What is the
probability of getting a number higher than 4 when you roll a die?
a. 1/6
b. 2/6 (or 1/3)
c. 4/6 (or 2/3)
(Hint: how many numbers are there on a die that are higher than 4? Divide
this number by the total number of sides on a die).
Answer: b: 2/6 (or 1/3)
Hint: how many numbers are there on a die that are higher than 4? There
are two numbers, namely 5 and 6. Divide this number (i.e. two) by the total
number of sides on a die, i.e. six.
Activity 2: - simple slot machine
2. Sipho is going to spin the arrow on a four coloured wheel that has four equal
area segments: blue, green, yellow and red. Sipho bets on the colour blue.
What is the probability that Sipho will win and that the arrow will stop on blue?
a. 1/4
b. 2/4 ( or 1/2)
(Hint: How many colour blues are there on the wheel? Divide this number by
the total number of colours on the wheel.)
Answer: a. 1 in 4
Hint: How many blue coloured segments are there on the wheel? There is only
one blue coloured segment. Divide this number by the total number of
coloured segments on the wheel. There are four coloured segments in
all. The probability of Sipho guessing correctly is 1/4 (or 25%).
Activity 3 - roulette wheel
3. A roulette wheel has 37 numbers: 18 black, 18 red and a green “0”. Of the
37 numbers, 18 are even and 18 are uneven (or odd), and then there's
“0”.When the wheel is spun, all numbers are equally likely to appear.
2.
Learning Activity 9.3 with Answers
Grade 9 | Unit 9.3 | Page 13
On a single spin of the wheel, what is the probability that the ball will
land on your bet of a black number?
a. 1/2
b. 1/18
c. 18/19
d. 18/37
(Hint: divide the number of black numbers by the total number of numbers on
the wheel)
Answer: d. 18 /37
Hint: divide the number of black numbers by the total numbers on the wheel.
There are eighteen black numbers on the wheel and thirty-seven numbers
in all. The probability is therefore 18/37 that the wheel will stop on a black
number.
4. On a single spin of the wheel, what is the probability that the ball will land
on “0”?
a. 1/18
b. 1/2
c. 1/37
(Hint: how many “0” numbers are there? Divide this by the total number of
numbers on the roulette wheel.)
Answer: c: 1/37
There is only one “0” and thirty-seven numbers in all. The probability that
the wheel will stop on “0” is therefore 1/37
5. And here is a tricky one: On a single spin of the wheel, what is the probability
that the ball will land on an even number less than 9?
a. 9/37
b. 36/37
c. 1/37
d. 4/37
(Hint: first of all determine how many even numbers less than 9 there are. Then
divide this number by the total number of numbers on the roulette wheel.)
Answer: d. 4/37
Hint: first of all determine how many even numbers less than 9 there are. There
are four even numbers less than 9, namely {8, 6, 4, 2}. Then
divide this number by the total number of numbers on the roulette wheel, i.e.
thirty-seven numbers. The probability is therefore 4/37.)
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