SHS1 Additional Mathematics · Semester 2, Week 18

Making Predictions with Data

Lesson notes

Learning Objectives

Indicator: 1.4.2.LI.2 - Discuss the concepts of permutation and combination and use them to solve real life problems.

By the end of the lesson, learners can:

  1. Define permutation as an ordered arrangement of objects and combination as a selection where order does not matter, and state the key difference between them.
  2. Use the formula nPr = n! / (n - r)! to calculate the number of permutations of r objects selected from n distinct objects, showing full working.
  3. Calculate the number of arrangements of n objects that include identical or repeated elements using n! / (r1! × r2! × … × rk!).
  4. Calculate the number of circular arrangements of n distinct objects using (n - 1)!.
  5. Solve real-life problems set in everyday Ghanaian situations that require choosing between permutation and combination reasoning.

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Curriculum details

Strand
Handling Data (Strand 4)
Sub-strand
Making Predictions with Data (4.2)
Content standard
1.4.2.CS.1 - Demonstrate knowledge of basic principles of permutation and combination and interpret probability in everyday life. 1.4.2.LO.1 Explain combination and permutation, state their difference and solve basic problems related to permutation and combination. 1.4.2.LO.2 Explain the terminologies in probability orally and find the relative frequency in a given experiment.
Indicator
1.4.2.LI.2 - Discuss the concepts of permutation and combination and use them to solve real life problems.
Suggested placement
Semester 2, Week 18 (Week 38 of the year)

Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.

Curriculum reference
NaCCA curriculum document, p. 244

Exemplars (from the NaCCA curriculum)

Collaborative Learning, Initiate Talk for Learning and Talk for Learning Approaches, Problem-based learning,
Learning Experience: Learners to discuss the types and features of different permutations (circular arrangements, identical elements etc.), and what happens when terms of ordered and un-ordered arrangements and special arrangements are used.
Activity 1: Ordered arrangements: Initiate Talk for Learning, Experiential and Collaborative learning Approaches to support learners to explore how ordered arrangements can be counted.
Learners think-pair-square to brainstorm and discuss situations where they have to arrange a set of objects in which the order of appearance of elements of the set matters. For instance, APC differs from PAC.
Example: Three students, Esi, Abiba and Makafui, are contesting for 1st, 2nd and 3rd positions in a marathon race.
Using the first letters of their names, the possible arrangements are: EAM, AEM, EMA, MEA, MAE, and AME. Learners, in convenient groups, work together on different examples to establish that permutation is an ordered arrangement of objects in a row. It is a selection of groups of objects in which order is important.
Example: Kweku has 4 different mathematisc books on his shelf. Find the number of orders in which the 4 books can be arranged on the shelf.
Solution: There will be 4 choices in the first slot. There will be 3 choices in the first slot. There will be 2 choices in the first slot. There will be 1 choice in the first slot. ∴ There are 4 × 3× 2 × 1=24 possible arrangements of Kweku's books on the shelf.
Learners recognise that the number of permutations of n objects is denoted n! and use it to solve related problems.
Example: Kweku has 4 different mathematics books on his shelf. Find the number of orders in which the 4 books can be arranged on the shelf.
Solution: There are 4! Ways to arrange the four books hence 4! = 4 ×3× 2× 1=24 ways Kweku can arrange the mathematics books.
Activity 2: Permutation formula Initiate Talk for Learning, Experiential and Collaborative learning Approaches to support learners to use the permutation formula to solve related problems. Learners think-pair-square to brainstorm and discuss facts about permutation, selection of items out of a given set and unordered arrangement of things. Learners establish that the number of ways in which r items can be selected out from a set n items in which order matters is given by the formula: nPr =P(n,r)=n!/(n-r)! = n(n-1)(n-2)(n-3)...[n-(r-1)]
Example: Evaluate the permutation 5 P 3 Solution: 5 P 3 = P(5,3)=5!/(5-3)!=60
Activity 3: Permutation with identical/repeated objects Initiate Talk for Learning, Experiential and Collaborative learning Approaches to support learners to use the permutation formula to solve related problems. Learners establish that the number of ways of arranging n objects where different r's of them are of the same kind is given by: n!/(r1!.r2!.r3!.....rk!)
Example: In how many ways can the letters in the word SECRETS be arranged?
Solution: The number of letters is 5, so n=5; S and E are repeated, so the permutation will be affected by 2×2! Therefore, the required number of ways is 5!/(2! ×2!)= 30 ways.
Activity 4: Permutation with identical/repeated Objects Initiate Talk for Learning, Experiential and Collaborative learning Approaches to support learners to use the permutation formula to solve related problems.
Learners work in groups and, through role play (acting out), establish/discover that the number of ways of arranging objects in a circle is (n-1)! Example: In how many different ways can 6 people sit at a circular table? Solution: The number of persons is 6, so n=6; since they are to sit in a circle, we have (6- 1)!=5!=5×4×3×2×1=120 ways.
Teaching and Learning Resources:
- Ludo dice, coins, playing cards, objects in a sac or bowl.
- YEAR TWO
Assessment (1.4.2.AS.2). The document marks these depth-of-knowledge levels for this indicator: Level 1 Recall; Level 2 Skills of conceptual understanding; Level 3 Strategic reasoning; Level 4 Extended critical thinking and reasoning.