SHS1 Additional Mathematics · Semester 2, Week 18

Making Predictions with Data

Lesson notes

Learning Objectives

Indicator: 1.4.2.LI.3 - Distinguish between the concepts of permutation and combination and establish the relationship between them.

By the end of the lesson, learners can:

  1. Explain, in their own words, the difference between ordered arrangements (permutations) and un-ordered selections (combinations), giving one example of each.
  2. State and use the combination formula nCr = n!/[r!(n - r)!] to count the number of ways of selecting r objects from n distinct objects.
  3. State and use the relationship nCr = nPr / r! to convert between permutation and combination values.
  4. Solve multi-step counting problems that combine the fundamental counting principle with the combination formula, such as forming committees with specified numbers of men and women.
  5. Justify their answers in words, explaining why order matters or does not matter in a given counting situation.

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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.3 - Distinguish between the concepts of permutation and combination and establish the relationship between them.
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. 247

Exemplars (from the NaCCA curriculum)

Collaborative Learning, Initiate Talk for Learning and Talk for Learning Approaches, Problem-based learning, Experiential Learning
Learning Experience: Learners to discuss the types and features of different permutations (circular arrangements, identical elements, etc.). What happens when terms of ordered and un-ordered arrangements and special arrangements.
Activity 1: Ordered and un-ordered arrangements
- Initiate Talk for Learning, Experiential and Collaborative learning Approaches to support learners to distinguish between ordered and un-ordered choices.
- 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 does not matter. For instance, APC is not different from PAC, because both sets have the same elements.
- Learners work in their groups to make presentations by comparing, contrasting and debating with other groups on ordered arrangements of items and un-ordered arrangements of items
- Learners discover/establish that the number of subsets of r elements that can be formed from elements is nCr =(n¦r)= n!/r!(n-r)!
Example 1: In how many ways can a committee of 3 members be formed from a team of 8 people? Solution 8 C 3 =(8¦3)= 8!/3!(8-3)!=56
Example 2: There are 6 different coloured cubes in a bag. In how many ways can Mawuli draw a set of 3 cubes from the bag?
Activity 2: Combination as a way of counting
- Initiate Talk for Learning, problem-based, Experiential and Collaborative learning Approaches to support learners to use combination formulas in different contexts.
- Learners explore situations where fundamental principles of counting along with the combination formula are used to solve counting problems.
- Learners find the number of ways of selecting r objects from a collection with a given condition.
Example: How many committees consisting of 2 women and 1 man can be formed from a group of 4 women and 2 men?
Solution: Task 1: Selecting 2 women from 4 women can be done in 4C2 ways.
Task 2: Selecting 1 man from 2 men can be done in 2C1 ways.
Task 1 followed by task 2 can be accomplished in 4 C 2 × 2 C 1 = 6×2 = 12 ways
Activity 3: Relationship between combination and permutation formulae Initiate Talk for Learning, problem-based, Experiential and Collaborative learning Approaches to support learners in using the relationship between combinations and permutation formulas to Solve problems Learners discover/establish that nCr =(n¦r)= n!/r!(n-r)!= nPr/r! and use it to solve problems.
Example 1: Find the value of n if i) nP 3 /nC 4 = 24/5 ii) nC 5 /nP 4 = 1/4
Teaching and Learning Resources:
- Ludo dice, coins, playing cards, objects in a sac or bowl.
- YEAR TWO
Assessment (1.4.2.AS.3). The document marks these depth-of-knowledge levels for this indicator: Level 1 Recall; Level 2 Skills of conceptual understanding; Level 4 Extended critical thinking and reasoning.