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P6

Enumerate sets and combinations of sets systematically, using tables, grids, Venn diagrams and tree diagrams

Venn diagrams and tables

Worked answers, methods and verified real exam appearances for P6 on Edexcel GCSE Maths 1MA1.

Explanation

  • Systematic enumeration means listing every permitted outcome once in a clear order.
  • Use a table or grid when two quantities vary, a tree for successive choices, and a Venn diagram for overlapping sets.
  • For a two-set Venn diagram, fill the intersection first, then the regions belonging only to each set, then the outside region.
  • A list of possible outcomes does not automatically make them equally likely; probability still depends on how the experiment works.

Worked example

List the numbers from 11 to 2020 that are multiples of 33 or 55 by separating the intersection and the two 'only' regions.

  1. 1.Both: {15}\{15\}.
  2. 2.Multiples of 33 only: {3,6,9,12,18}\{3,6,9,12,18\}.
  3. 3.Multiples of 55 only: {5,10,20}\{5,10,20\}.

Answer: {3,5,6,9,10,12,15,18,20}\{3,5,6,9,10,12,15,18,20\}.

Common mistakes

  • Don't fall into the trap of missing an outcome or listing the same outcome twice.
  • Don't fall into the trap of placing intersection values in both 'only' regions as well.

Exam tip

Choose a fixed order and count your final outcomes as a check.

Worked practice

Q1
Tier 1 · Easy

1

A uniform is made from one of two shirts, blue or white, and one of three ties, red, silver or green. List all possible shirt-and-tie combinations.

(2)

(Total for Question 1 is 2 marks)

Mark scheme

Mark scheme for question 1
QuestionAnswerMarkMark scheme
1
  • Blue-red, blue-silver, blue-green, white-red, white-silver, white-green.
2Hold the shirt colour fixed and list every tie, then repeat for the other shirt. This gives 2×3=62\times3=6 combinations, each appearing once.
Q2
Tier 2 · Standard

2

The universal set is the integers from 11 to 2020. Set A contains the multiples of 33 and set B contains the factors of 1818. Enumerate the four regions of a Venn diagram for A and B.

(4)

(Total for Question 2 is 4 marks)

Mark scheme

Mark scheme for question 2
QuestionAnswerMarkMark scheme
2
  • AB={3,6,9,18}A\cap B=\{3,6,9,18\}.
  • A only ={12,15}=\{12,15\}; B only ={1,2}=\{1,2\}.
  • Neither ={4,5,7,8,10,11,13,14,16,17,19,20}=\{4,5,7,8,10,11,13,14,16,17,19,20\}.
4List A={3,6,9,12,15,18}A=\{3,6,9,12,15,18\} and B={1,2,3,6,9,18}B=\{1,2,3,6,9,18\}. Put their common values in the intersection, remove these to find each 'only' region, then place every unused integer from 11 to 2020 outside both circles.
Q3
Tier 3 · Hard

3

A three-digit number is formed from three different digits chosen from 11, 22, 33 and 44. Enumerate all the numbers that are greater than 230230 and even. How many of these numbers do not contain the digit 11?

(4)

(Total for Question 3 is 4 marks)

Mark scheme

Mark scheme for question 3
QuestionAnswerMarkMark scheme
3
  • 234,312,314,324,342,412,432234,312,314,324,342,412,432.
  • 44 of these numbers do not contain the digit 11.
4Work systematically by hundreds digit. Starting with 22 gives 234234; starting with 33 gives 312,314,324,342312,314,324,342; starting with 44 gives 412,432412,432. The values without digit 11 are 234,324,342,432234,324,342,432, so there are 44.
Q4
Tier 1 · Easy

4

Write down all the ordered pairs of positive integers that have a total of 77 and have the first number less than the second number.

(2)

(Total for Question 4 is 2 marks)

Mark scheme

Mark scheme for question 4
QuestionAnswerMarkMark scheme
4
  • (1,6),(2,5),(3,4)(1,6),(2,5),(3,4)
2Start with first number 11 and increase it systematically: (1,6),(2,5),(3,4)(1,6),(2,5),(3,4). The next pair would have the first number greater than the second, so the list is complete.
Q5
Tier 2 · Standard

5

A journey uses either a bus or a train, followed by walking, cycling or taking a taxi. A bus journey cannot be followed by a taxi. List all the possible journeys and write down how many there are.

(3)

(Total for Question 5 is 3 marks)

Mark scheme

Mark scheme for question 5
QuestionAnswerMarkMark scheme
5
  • Bus-walk, bus-cycle, train-walk, train-cycle, train-taxi.
  • 55 journeys.
3List every second stage after bus, omitting taxi, then list every second stage after train. This gives 2+3=52+3=5 permitted journeys.
Q6
Tier 3 · Hard

6

The universal set is the integers from 11 to 3030. Set A contains multiples of 22, set B contains square numbers, and set C contains factors of 2424. List the integers in each region that is in exactly two of the three sets and work out how many integers are in exactly two sets.

(4)

(Total for Question 6 is 4 marks)

Mark scheme

Mark scheme for question 6
QuestionAnswerMarkMark scheme
6
  • A and B only: {16}\{16\}; A and C only: {2,6,8,12,24}\{2,6,8,12,24\}; B and C only: {1}\{1\}.
  • 77 integers are in exactly two sets.
4The only number in all three sets is 44, so exclude it from the exactly-two regions. The remaining common values are 1616 in A and B, 2,6,8,12,242,6,8,12,24 in A and C, and 11 in B and C. There are 1+5+1=71+5+1=7 integers.
Q7
Tier 2 · Standard

7

The first coordinate of an ordered pair is chosen from {2,1,4}\{-2,1,4\} and the second coordinate is chosen from {1,3}\{-1,3\}. List all the possible ordered pairs. Then list the pairs for which the sum of the coordinates is greater than 22.

(3)

(Total for Question 7 is 3 marks)

Mark scheme

Mark scheme for question 7
QuestionAnswerMarkMark scheme
7
  • (2,1),(2,3),(1,1),(1,3),(4,1),(4,3)(-2,-1),(-2,3),(1,-1),(1,3),(4,-1),(4,3).
  • Sum greater than 22: (1,3),(4,1),(4,3)(1,3),(4,-1),(4,3).
3Fix the first coordinate at 2-2, then 11, then 44, pairing each with both possible second coordinates. Check the coordinate sums; only 1+31+3, 4+(1)4+(-1) and 4+34+3 are greater than 22.
Q8
Tier 3 · Hard

8

A ticket code consists of one letter, A, B or C, followed by two different digits chosen from 11, 22, 33 and 44. For an A-code, the final digit must be even. For a B-code, the two digits must have a total of 55. For a C-code, the first digit must be less than the second digit. List every permitted code and work out the total number of codes.

(4)

(Total for Question 8 is 4 marks)

Mark scheme

Mark scheme for question 8
QuestionAnswerMarkMark scheme
8
  • A-codes: A12, A32, A42, A14, A24, A34.
  • B-codes: B14, B41, B23, B32.
  • C-codes: C12, C13, C14, C23, C24, C34.
  • 1616 permitted codes.
4For A, fix the last digit as 22 or 44 and choose any different first digit, giving 66 codes. The ordered digit pairs totalling 55 are 14,41,23,3214,41,23,32, giving 44 B-codes. The increasing pairs are 12,13,14,23,24,3412,13,14,23,24,34, giving 66 C-codes. The total is 6+4+6=166+4+6=16.
Q9
Tier 3 · Hard

9

A robot makes exactly five moves. Each move is either one square east, E, or one square north, N. It must make three east moves and two north moves, but it must not make two north moves consecutively. List every permitted route and work out how many there are.

(3)

(Total for Question 9 is 3 marks)

Mark scheme

Mark scheme for question 9
QuestionAnswerMarkMark scheme
9
  • NENEE, NEENE, NEEEN, ENENE, ENEEN, EENEN; 66 routes.
3Place the two N moves systematically in non-adjacent positions among the five moves, then fill the other positions with E. The possible N-position pairs are (1,3),(1,4),(1,5),(2,4),(2,5),(3,5)(1,3),(1,4),(1,5),(2,4),(2,5),(3,5), giving the six listed routes and no repeats.
Q10
Tier 3 · Hard

10

A club chooses a captain and a deputy from students A, B, C, D and E. The same student cannot hold both roles. Student C cannot be captain, and students A and B cannot both hold a role. List every possible ordered captain-deputy pair and work out the total number of choices.

(5)

(Total for Question 10 is 5 marks)

Mark scheme

Mark scheme for question 10
QuestionAnswerMarkMark scheme
10
  • AC, AD, AE; BC, BD, BE; DA, DB, DC, DE; EA, EB, EC, ED.
  • 1414 choices.
5List by captain. With A as captain, B is excluded and the deputy can be C, D or E; similarly there are three choices with B as captain. With D or E as captain, any of the other four students can be deputy because A and B are not then serving together. This gives 3+3+4+4=143+3+4+4=14.

Verified exam appearances

SeriesPaperQuestionMarksCalculatorTierLinks
2023-061FQ245Non-calculatorFoundationQPMS
2024-063FQ274AllowedFoundationQPMS
2024-063HQ64AllowedHigherQPMS
2022-062HQ166AllowedHigherQPMS
2021-111HQ23Non-calculatorHigherQPMS
2022-113HQ64AllowedHigherQPMS
2021-111FQ213Non-calculatorFoundationQPMS
2024-111FQ115Non-calculatorFoundationQPMS
2019-063HQ15AllowedHigherQPMS
2019-063FQ245AllowedFoundationQPMS
2024-061HQ43Non-calculatorHigherQPMS
2019-113FQ204AllowedFoundationQPMS
2024-112FQ232AllowedFoundationQPMS
2023-112HQ214AllowedHigherQPMS
2024-061FQ233Non-calculatorFoundationQPMS
2024-112HQ42AllowedHigherQPMS

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