REAL NUMBER SYSTEM
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Subject: Mathematics
Class: SHS 1
Term: 1st Term
Week: 5
Grade code: 1.1.1.LI.3
Strand code: 1
Sub-strand code: 1
Content standard code: 1.1.1.CS.2
Indicator code: 1.1.1.LI.3
Theme: NUMBERS FOR EVERYDAY LIFE
Subtheme: REAL NUMBER SYSTEM
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This lesson extends our understanding of sets from two overlapping groups to three. In our daily lives in Ghana, we often categorise things into more than two groups. For example, a student might be a member of the Debating Club, the Science Club, and the School Choir. A farmer in the Volta Region might grow maize, cassava, and yams. Understanding how these groups overlap helps us to analyse information accurately, make better decisions, and solve complex real-world problems. Today, we will explore the properties, laws, and formulas that govern the relationships between three sets, using Venn diagrams and algebra to make sense of them.
Part 1: The Three-Set Venn Diagram (15 mins)
A Venn diagram for three intersecting sets (A, B, and C) within a universal set (U) has 8 distinct regions. Let's understand what each region represents. Region 1 (A only): Elements in A, but not in B or C. Symbol: `A ∩ B' ∩ C'` Region 2 (B only): Elements in B, but not in A or C. Symbol: `A' ∩ B ∩ C'` Region 3 (C only): Elements in C, but not in A or B. Symbol: `A' ∩ B' ∩ C` Region 4 (A and B only): Elements in both A and B, but not in C. Symbol: `A ∩ B ∩ C'` Region 5 (A and C only): Elements in both A and C, but not in B. Symbol: `A ∩ B' ∩ C` Region 6 (B and C only): Elements in both B and C, but not in A. Symbol: `A' ∩ B ∩ C` Region 7 (A and B and C): Elements in all three sets. Symbol: `A ∩ B ∩ C` Region 8 (Neither A, B, nor C): Elements in the universal set U, but not in any of A, B, or C. Symbol: `(A ∪ B ∪ C)'` or `A' ∩ B' ∩ C'`
Key Strategy for Word Problems: When filling a three-set Venn diagram from a word problem, always start from the innermost region (Region 7: the intersection of all three sets) and work your way outwards.
Part 2: Set Identities and Laws (25 mins)