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Introduction to Probability

In this worksheet, students practise using words to describe probability.

'Introduction to Probability' worksheet

Key stage:  KS 4

GCSE Subjects:   Maths

GCSE Boards:   AQA, Eduqas, Pearson Edexcel, OCR

Curriculum topic:   Probability

Curriculum subtopic:   Probability, Basic Probability and Experiments

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

What is probability?

Probability in maths is the area that deals with the chance of something happening.

 

What words do we use to describe probability?

 

There are 7 terms we use to describe probability;

Impossible: There is no way this can happen (Example: A man growing to be 200 ft tall)

Very Unlikely: This will probably not happen but could (Example: Winning the lottery)

Unlikely: This has more chance of not happening than it does of happening (Example: Rolling a six on a dice)

Evens: This has two things that could happen that are equally likely (Example: Tossing a coin and getting a head)

Likely: This has more chance of happening than it does of not happening (Example: Picking a consonant of the alphabet at random)

Very Likely: This will probably happen but might not (Example: Using your phone today before you go to bed)

Certain: This has to happen (Example: Rolling a normal dice and getting a number less than 7)

 

When do I use words to describe probability?

 

Most probability is described using a number so you should only use words if the question specifically asks you to.

 

Match the situation with the word you would use to describe the chance of it happening.

Column A

Column B

You will watch some tv tonight
Certain
You will live to be 100
Unlikely
Christmas day will be on the 25th December
Evens
A new born baby will be a boy
Likely

What word would you use to describe...

 

The chance of you having an English lesson today.

Likely

Certain

What word would you use to describe...

 

Picking a card out of a deck of normal playing cards and getting a card with a red symbol.

Likely

Evens

What word would you use to describe the chance of picking a red ball out of a bag containing only red balls.

Which of these two events is more likely?

 

Event A: Rolling a normal dice and getting a number less than 7.

Event B: Rolling a normal dice and getting an odd number.

Event A

Event B

Which of these two events is less likely

 

I have a bag with 7 red balls and 3 black balls:

 

Event A: Pulling out a black ball

Event B: Pulling out a yellow ball

Event A

Event B

Is there an even chance that it will rain tomorrow?

Yes

No

Does the probability word correctly describe the situation?

Which of these events are likely?

Winning the lottery

A child eating cereal for breakfast tomorrow

You will live to be 50

Use your understanding of probability so far to answer the question below.

 

Winning the lottery

A child eating cereal for breakfast tomorrow

You will live to be 50

  • Question 1

Match the situation with the word you would use to describe the chance of it happening.

CORRECT ANSWER

Column A

Column B

You will watch some tv tonight
Likely
You will live to be 100
Unlikely
Christmas day will be on the 25th...
Certain
A new born baby will be a boy
Evens
EDDIE SAYS
You have to remember that this question is not actually talking about you, it's talking about a general person. Don't fall down on thinking, but 'I watch telly every night so it's certain'. Not quite, it's likely but there are a number of ways you could end up not watching telly so it's not certain.
  • Question 2

What word would you use to describe...

 

The chance of you having an English lesson today.

CORRECT ANSWER
Likely
EDDIE SAYS
Remember, we are thinking about the average person in this age group. We can't possibly know everyone's timetables, but we can work out that this cannot be certain, as there are two days in a week where this would certainly not be the case. Do you have to have an English lesson every day? What about Saturday and Sunday?
  • Question 3

What word would you use to describe...

 

Picking a card out of a deck of normal playing cards and getting a card with a red symbol.

CORRECT ANSWER
Evens
EDDIE SAYS
What did you think? A deck of cards has exactly 26 red cards and 26 black cards so it's exactly half that are red. This gives an even chance. Can you see that?
  • Question 4

What word would you use to describe the chance of picking a red ball out of a bag containing only red balls.

CORRECT ANSWER
Certain
EDDIE SAYS
It's all about using the correct language when doing probability! If there's only red balls in there, you have to pull out a red ball. Are you getting more used to this vocabulary?
  • Question 5

Which of these two events is more likely?

 

Event A: Rolling a normal dice and getting a number less than 7.

Event B: Rolling a normal dice and getting an odd number.

CORRECT ANSWER
Event A
EDDIE SAYS
How did you do? Event A has to happen as the numbers go up to 6. You can't have anything that is more likely to happen than certain, so this one has to be the more likely one.
  • Question 6

Which of these two events is less likely

 

I have a bag with 7 red balls and 3 black balls:

 

Event A: Pulling out a black ball

Event B: Pulling out a yellow ball

CORRECT ANSWER
Event B
EDDIE SAYS
Did you read the question carefully? Event B can't happen (there aren't any yellow balls in the bag) so this one has to be the least likely.
  • Question 7

Is there an even chance that it will rain tomorrow?

CORRECT ANSWER
No
EDDIE SAYS
This was a tricky one. This is a really common mistake. There are only two things that could happen but they aren't equally likely to happen so it isn't an even chance. Remember just like when we consider the average person we are considering the average day. A day is dry or rainy, but it isn't equally likely. Think about dry days, it could be misty, foggy, freezing, sunny, cloudy. If we said it was equally likely we would be suggesting that it rains on 182.5 days of the year... and although it feels like it sometimes, it does not!
  • Question 8

Does the probability word correctly describe the situation?

CORRECT ANSWER
EDDIE SAYS
These words are all valid. Remember, when we are answering these questions on probability we are not asking them to an individual although we word them as 'you', we are thinking about the average person. You may have a day where for some reason you do not eat, but if you think about the average person, it is certain that they will eat in a day.
  • Question 9

Which of these events are likely?

CORRECT ANSWER
A child eating cereal for breakfast tomorrow
You will live to be 50
EDDIE SAYS
The only one here that isn't likely is for you to win the lottery (if we ignore the fact you're probably too young to play it). The other two are likely events. How are you feeling about probability now?
  • Question 10

Use your understanding of probability so far to answer the question below.

 

CORRECT ANSWER
EDDIE SAYS
This is a key fact. Most probability is described using a number so you should only use words if the question says to.
---- OR ----

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