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N5

Apply systematic listing strategies, including use of the product rule for counting (m ways of doing one task and n ways of doing another gives m × n ways in total)

Listing strategies

Worked answers, methods and verified real exam appearances for N5 on Edexcel GCSE Maths 1MA1.

Explanation

  • A systematic listing strategy fixes one choice and cycles through every permitted second choice before moving on. Use a clear order, such as increasing digits or alphabetical letters, so you can see that no result is missing or repeated.
  • When order matters, AB and BA are different outcomes; when order does not matter, list each pair only once.
  • A table or tree can organise several stages.
  • Higher tier: if one task can be completed in mm ways and a following independent choice in nn ways, the product rule gives m×nm\times n combined outcomes.
  • Examiners award completeness only when the structure of the list is evident.

Worked example

Higher tier: Three different digits are chosen from 22, 44, 55 and 77 to make an even three-digit number. How many numbers are possible?

  1. 1.Fix the final digit as 22: choose and order two of the remaining three digits, giving 3×2=63\times2=6 numbers.
  2. 2.Fix the final digit as 44: again there are 3×2=63\times2=6 numbers.
  3. 3.Add the two disjoint cases: 6+6=126+6=12.

Answer: 1212 even numbers.

Common mistakes

  • Don't change two positions at once and omit a valid outcome.
  • Don't count AB and BA twice when the question says order does not matter.
  • Don't use the product rule even though later choices depend on earlier restrictions.

Exam tip

Group a list by one fixed position or case; an unstructured collection may not earn the method mark for systematic listing.

Worked practice

Q1
Tier 1 · Easy

1

A badge uses one of the letters A, B or C and one of the numbers 11, 22 or 33. List every possible badge code in a systematic order.

(2)

(Total for Question 1 is 2 marks)

Mark scheme

Mark scheme for question 1
QuestionAnswerMarkMark scheme
1
  • A1, A2, A3, B1, B2, B3, C1, C2, C3
2Hold the letter fixed while cycling through the numbers: A1, A2, A3; then B1, B2, B3; then C1, C2, C3. This gives all 99 codes once each.
Q2
Tier 2 · Standard

2

A three-digit number is made using three different digits from 22, 44, 55 and 77. List all the possible even numbers.

(3)

(Total for Question 2 is 3 marks)

Mark scheme

Mark scheme for question 2
QuestionAnswerMarkMark scheme
2
  • 452452, 472472, 542542, 572572, 742742, 752752, 254254, 274274, 524524, 574574, 724724, 754754
3List by the final digit. Ending in 22 gives 452452, 472472, 542542, 572572, 742742, 752752. Ending in 44 gives 254254, 274274, 524524, 574574, 724724, 754754. The fixed final digit makes the list systematic and complete.
Q3
Tier 3 · Hard

3

Two different numbers are selected from 11, 22, 33, 44 and 55. The order of selection does not matter. List every pair whose product is even and whose sum is greater than 55.

(3)

(Total for Question 3 is 3 marks)

Mark scheme

Mark scheme for question 3
QuestionAnswerMarkMark scheme
3
  • (2,4)(2,4), (2,5)(2,5), (3,4)(3,4), (4,5)(4,5)
3List unordered pairs in rows beginning with 11, then 22, then 33, then 44. Reject pairs with an odd product or sum at most 55. The pairs left are (2,4)(2,4), (2,5)(2,5), (3,4)(3,4) and (4,5)(4,5).
Q4
Tier 1 · Easy

4

Use two different digits from 11, 22 and 33 to make a two-digit number. List all the possible numbers.

(2)

(Total for Question 4 is 2 marks)

Mark scheme

Mark scheme for question 4
QuestionAnswerMarkMark scheme
4
  • 12,13,21,23,31,3212,13,21,23,31,32
2Fix the tens digit in turn. Starting with 11 gives 12,1312,13; starting with 22 gives 21,2321,23; starting with 33 gives 31,3231,32.
Q5
Tier 2 · Standard

5

A route uses gate A or gate B, followed by lane 11, 22 or 33. Lane 33 is closed after gate B. List all the possible routes.

(2)

(Total for Question 5 is 2 marks)

Mark scheme

Mark scheme for question 5
QuestionAnswerMarkMark scheme
5
  • A1, A2, A3, B1, B2
2Hold the gate fixed. Gate A gives A1, A2 and A3. Gate B would give B1, B2 and B3, but B3 is unavailable, leaving B1 and B2.
Q6
Tier 3 · Hard

6

One spinner is labelled 11, 22, 44 and another is labelled 11, 33. Both spinners are spun once. List all the possible totals. Write each total once. You must show all your working.

(2)

(Total for Question 6 is 2 marks)

Mark scheme

Mark scheme for question 6
QuestionAnswerMarkMark scheme
6
  • 2, 3, 4, 5, 72,\ 3,\ 4,\ 5,\ 7
2Fix the result on the first spinner. With 11, the totals are 2,42,4; with 22, they are 3,53,5; with 44, they are 5,75,7. This records all six outcomes, so the possible totals are 2,3,4,5,72, 3, 4, 5, 7.
Q7
Tier 2 · Standard

7

An appointment can start at 10:0010{:}00, 10:3010{:}30 or 11:0011{:}00 and can last 3030 minutes or 6060 minutes. It must finish by 11:3011{:}30. List all the possible start-time and duration pairs.

(3)

(Total for Question 7 is 3 marks)

Mark scheme

Mark scheme for question 7
QuestionAnswerMarkMark scheme
7
  • 10:0010{:}00 and 3030 minutes; 10:0010{:}00 and 6060 minutes; 10:3010{:}30 and 3030 minutes; 10:3010{:}30 and 6060 minutes; 11:0011{:}00 and 3030 minutes
3List both durations for 10:0010{:}00 and both for 10:3010{:}30. At 11:0011{:}00, only the 3030-minute appointment finishes by 11:3011{:}30; a 6060-minute appointment finishes too late. This gives five pairs.
Q8
Tier 3 · Hard

8

An outfit has one jacket, one pair of trousers and one pair of shoes. The jackets are black and grey. The trousers are navy, cream and khaki. The shoes are boots and trainers. The grey jacket is never worn with the khaki trousers, and the navy trousers are never worn with the trainers. List all the possible outfits.

(4)

(Total for Question 8 is 4 marks)

Mark scheme

Mark scheme for question 8
QuestionAnswerMarkMark scheme
8
  • black-navy-boots; black-cream-boots; black-cream-trainers; black-khaki-boots; black-khaki-trainers; grey-navy-boots; grey-cream-boots; grey-cream-trainers
4Hold the jacket and trousers fixed, then test both pairs of shoes. The black jacket gives five outfits: navy-boots, both cream outfits and both khaki outfits. The grey jacket gives three outfits: navy-boots and both cream outfits. The restrictions remove every grey-khaki outfit and each navy-trainers outfit.
Q9
Tier 3 · Hard

9

Higher only: A light signal uses one of four colours, one of three patterns and one of two durations. A red signal can use only the steady pattern. The other colours can use any pattern. Work out the total number of different signals.

(4)

(Total for Question 9 is 4 marks)

Mark scheme

Mark scheme for question 9
QuestionAnswerMarkMark scheme
9
  • 2020 signals
4For each of the three non-red colours there are 3×2=63\times2=6 pattern-duration choices, giving 3×6=183\times6=18 signals. Red has one pattern and two durations, giving 22 more. The total is 18+2=2018+2=20.
Q10
Tier 3 · Hard

10

A robot reaches its target by making exactly three moves east and two moves north. It can make the five moves in any order. Work out the number of different routes. You must show a systematic method.

(4)

(Total for Question 10 is 4 marks)

Mark scheme

Mark scheme for question 10
QuestionAnswerMarkMark scheme
10
  • 1010 routes
4List routes by the positions of the two north moves: NNEEE, NENEE, NEENE, NEEEN, ENNEE, ENENE, ENEEN, EENNE, EENEN and EEENN. This systematic list has 1010 different routes.

Verified exam appearances

SeriesPaperQuestionMarksCalculatorTierLinks
2024-112HQ142AllowedHigherQPMS
2023-112FQ92AllowedFoundationQPMS
2022-112FQ51AllowedFoundationQPMS
2021-113FQ72AllowedFoundationQPMS
2019-112HQ142AllowedHigherQPMS
2024-063HQ132AllowedHigherQPMS
2019-061HQ164Non-calculatorHigherQPMS
2024-062FQ102AllowedFoundationQPMS
2021-112HQ132AllowedHigherQPMS
2022-063HQ112AllowedHigherQPMS
2022-113HQ152AllowedHigherQPMS
2023-113HQ163AllowedHigherQPMS
2023-061HQ192Non-calculatorHigherQPMS
2019-111FQ112Non-calculatorFoundationQPMS

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