Unit 10 Section 1 : Basic Probability of One Event

This section covers finding the probability of individual events when an experiment has several equally likely outcomes.

Practice Questions

Work out the answer to each of these questions then click on the button marked Click on this button below to see the correct answer to see whether you are correct.

Practice Question 1
A tube of sweets contains 10 red sweets, 7 blue sweets, 8 green sweets and 5 orange sweets.
If a sweet is taken at random from the tube, what is the probability that it is:
(a) red
(b) orange
(c) green or red
(d) not blue

Practice Question 2
Nine balls, each marked with a number from 1 to 9, are placed in a bag and one ball is taken out at random. What is the probability that the number on the ball is:
(a) odd
(b) a multiple of 3
(c) a 5
(d) not a 7



Work out the answers to the questions below and fill in the boxes. Click on the Click this button to see if you are correct button to find out whether you have answered correctly. If you are right then will appear and you should move on to the next question. If appears then your answer is wrong. Click on to clear your original answer and have another go. If you can't work out the right answer then click on Click on this button to see the correct answer to see the answer.

Most of the questions below have fractions as answers.
Put the numerator in the top box and the denominator in the bottom box, like the one shown here:   
All fractions in your answers must be simplified (cancelled down).

Question 1
There are 16 girls and 8 boys in the tennis club. One of these is chosen at random to enter a competition.
What is the probability that a girl is chosen?
Question 2
A bag contains 8 blue balls, 7 green balls and 5 red balls. A ball is taken at random from the bag.
What is the probability that the ball is:
(a) red
(b) blue
(c) green
(d) not green
Question 3
A card is taken at random from a standard 52-card pack of playing cards.
What is the probability that it is:
(a) a seven
(b) a heart
(c) a red card
(d) a red six
Question 4
You roll a fair dice.
What is the probability that the number you get is:
(a) five
(b) an odd number
(c) a number greater than 1
(d) a multiple of 4
Question 5
Ishmail writes a computer program that produces at random one of these digits:
         0, 1, 2, 3, 4, 5, 6, 7, 8, 9
What is the probability that the program produces:
(a) an even number
(b) a multiple of 4
(c) a number less than 7
(d) a multiple of 5
Question 6
The police line up 10 people in an identity parade; only one of the people is the criminal.
A witness does not recognise the criminal and so chooses a person at random.
What is the probability that:
(a) the criminal is chosen
(b) the criminal is not chosen
Question 7
There are 18 boys and 17 girls in a class.
One of these pupils is selected at random to represent the class.
What is the probability that the pupil selected is a girl?
Question 8
In Hannah's purse there are three 1 coins, five 10p coins and eight 2p coins.
She takes a coin at random from her purse.
What is the probability that it is:
(a) a 1 coin
(b) a 2p coin
(c) not a 1 coin
(d) a 1 coin or a 10p coin
Question 9
Some of the children in a class write down the first letter of their surname on a card; these cards are shown below:

One of these cards is taken at random.
(a) What is the probability that the letter on it is:
(i) W
(ii) S or T
(iii) J or M
(iv) not H
(v) a vowel
(b) Which letter is the most likely to be chosen?
Write your answer as a CAPITAL letter.

Question 10
Rachel buys a new CD, on which is her favourite track, 8 other tracks she likes and 2 tracks that she does not like.
She sets her CD player to play at random.
What is the probability that the first track it plays is:
(a) Rachel's favourite
(b) a track that she likes
(c) a track that she does not like

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Produced by A.J. Reynolds August 2007