Grade 9 | Unit 9.3 | Page 12

Unit 9.3Learning 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 outcomestotal number of possible outcomes

Activity 1 - dice throwing1. 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. 1/6b. 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? Dividethis 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? Thereare two numbers, namely 5 and 6. Divide this number (i.e. two) by the totalnumber of sides on a die, i.e. six.

Activity 2: - simple slot machine2. 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. 1/4b. 2/4 ( or 1/2)(Hint: How many colour blues are there on the wheel? Divide this number bythe total number of colours on the wheel.)Answer: a. 1 in 4Hint: How many blue coloured segments are there on the wheel? There is onlyone blue coloured segment. Divide this number by the total number ofcoloured segments on the wheel. There are four coloured segments inall. The probability of Sipho guessing correctly is 1/4 (or 25%).

Activity 3 - roulette wheel3. 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.

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. 1/2b. 1/18c. 18/19d. 18/37(Hint: divide the number of black numbers by the total number of numbers onthe wheel)Answer: d. 18 /37Hint: divide the number of black numbers by the total numbers on the wheel.There are eighteen black numbers on the wheel and thirty-seven numbersin all. The probability is therefore 18/37 that the wheel will stop on a blacknumber.

4. On a single spin of the wheel, what is the probability that the ball will land on “0”?a. 1/18b. 1/2c. 1/37(Hint: how many “0” numbers are there? Divide this by the total number ofnumbers on the roulette wheel.) Answer: c: 1/37There is only one “0” and thirty-seven numbers in all. The probability thatthe 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 probabilitythat the ball will land on an even number less than 9?a. 9/37b. 36/37c. 1/37d. 4/37(Hint: first of all determine how many even numbers less than 9 there are. Thendivide this number by the total number of numbers on the roulette wheel.)Answer: d. 4/37Hint: first of all determine how many even numbers less than 9 there are. Thereare four even numbers less than 9, namely {8, 6, 4, 2}. Thendivide this number by the total number of numbers on the roulette wheel, i.e.thirty-seven numbers. The probability is therefore 4/37.)