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Grade 7 · Higher · free GCSE maths worksheet

Conditional probability with Venn diagrams

Set notation and intersections.

11 original questions, 50 marks. Print the worksheet, mark it with the answers sheet, and use the solutions to see every step written out by hand.

Worksheet PDFWorked solutions PDFAnswers PDF

The questions

1

A Venn diagram shows the numbers of students in a year group who take Art (A) and Music (M).

RegionNumber of students
A only12
A ∩ M (both)8
M only15
Neither5

A student is chosen at random from the 40 students.

Work out P(A | M), the probability that the student takes Art given that they take Music.

2 marks
Show answer
8/23
2

100 students were asked how they travel to school. The two-way table shows the results.

WalkBusCarTotal
Year 1018221050
Year 1112142450
Total303634100

A student is chosen at random.

Given that the student travels by bus, work out the probability that they are in Year 11.

2 marks
Show answer
14/36
3

A gym has 80 members.

47 members use the treadmill (T).

39 members use the weights (W).

21 members use both the treadmill and the weights.

  1. Complete the Venn diagram to show the number of members in each region.
  2. One of the 80 members is chosen at random. Work out the probability that this member uses neither the treadmill nor the weights.
ξTW
5 marks
Show answer
a) T only = 26, both = 21, W only = 18, neither = 15 b) 3/16
4

60 people were asked whether they have a dog (D) or a cat (C).

32 people have a dog.

27 people have a cat.

11 people have both a dog and a cat.

  1. Work out the number of people who have a dog but not a cat.
  2. Work out the number of people who have neither a dog nor a cat.
  3. One of the 60 people is chosen at random. Work out the probability that this person has a dog but not a cat.
5 marks
Show answer
a) 21 b) 12 c) 7/20
5

ξ = {1, 2, 3, ..., 30}

A = {multiples of 4}

B = {multiples of 6}

A number is chosen at random from ξ. Work out:

  1. P(A | B)
  2. P(B | A)
  3. P(B′ | A′)
5 marks
Show answer
a) 2/5 b) 2/7 c) 20/23
6

The Venn diagram regions for sets A and B contain these numbers of people:

A only: 7   A ∩ B: 5   B only: 8   outside both: 10

One of the people is chosen at random.

  1. Find P(A ∩ B).
  2. Find P(A′).
  3. Find P(A ∪ B).
ξAB75810
5 marks
Show answer
a) 1/6 (= 5/30) b) 3/5 (= 18/30) c) 2/3 (= 20/30)
7

100 people went to a music festival.

58 saw band X.

45 saw band Y.

23 saw both bands.

  1. Work out the number of people who saw neither band.
  2. One person who saw band X is chosen at random. Work out the probability that this person also saw band Y.
5 marks
Show answer
a) 20 b) 23/58
8

A and B are two events.

P(A) = 0.5, P(B) = 0.4 and P(A ∪ B) = 0.7

  1. Work out P(A ∩ B).
  2. Work out P(B | A).
4 marks
Show answer
a) 0.2 b) 0.4
9

There are 40 students in a year group.

The Venn diagram for drama (D) and music (M) shows:

D only: 10   D ∩ M: 8   M only: 12   neither: 10

Two of the students who do music are chosen at random, without replacement.

Work out the probability that both of these students also do drama.

ξDM1081210
5 marks
Show answer
1495
10

80 students were asked which sports they play from football (F), rugby (R) and cricket (C).

4 students play all three sports.

12 students play football and rugby.

10 students play football and cricket.

9 students play rugby and cricket.

36 students play football.

29 students play rugby.

25 students play cricket.

  1. Complete the Venn diagram to show the number of students in each region.
  2. One of the 80 students is chosen at random. Work out the probability that this student plays none of the three sports.
ξFRC
6 marks
Show answer
a) F only 18, R only 12, C only 10, F and R only 8, F and C only 6, R and C only 5, all three 4, none 17 b) 17/80
11

90 people were asked which streaming services they use from A, B and C.

5 people use all three services.

14 people use A and B.

11 people use A and C.

13 people use B and C.

40 people use A.

35 people use B.

30 people use C.

  1. Complete the Venn diagram to show the number of people in each region.
  2. One person who uses service A is chosen at random. Work out the probability that this person also uses service C.
ξABC
6 marks
Show answer
a) A only 20, B only 13, C only 11, A and B only 9, A and C only 6, B and C only 8, all three 5, none 18 b) 11/40

Every question here is original and written by Robinson Tuition. The grade follows the Edexcel grade descriptors and suits AQA and OCR too; this is not an exam-board paper.

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