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Published bySabrina Cameron Modified over 8 years ago
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Here are a 4cm by 6cm rectangle, a 12cm by 2 cm rectangle, and a 3cm by 8cm rectangle. What’s the same? What’s different? What’s the same, what’s different?
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These are both 4cm by 6cm rectangles. What’s the same? What’s different? What’s the same, what’s different?
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6cm 3.8cm 10cm 2cm 2.3 cm Each of these rectangles is 3cm by 8cm 8 × 3 ≡ 6 × 3 + 2 × 3
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Draw pictures to represent that A.16 × 6 ≡ 10 × 6 + 6 × 6 B.16 × 6 ≡ 12.5 × 6 + 3.5 × 6 C.16 × 6 ≡ 20 × 6 – 4 × 6 D.16 × 6 ≡ 16 × 2 + 16 × 4 E.16 × 6 ≡ ☐ × 3 F.16 × 6 ≡ ☐ × 4 Representing multiplication
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A.15 × 9 + 5 × 9 ≡ × 9 B. × 8 + 8 × 8 ≡ 17 × 8 C.17 × – × 5 ≡ 12 × 6 D.11 × 4.3 – × 4.3 ≡ 5 × E.21 × – ≡ 20 × 19 F.3.6 × + 7 × ≡ 36 G.15 × 9 + × 18 ≡ 21 × 9 H.7 × + × 6 ≡ 21 × 12 Representing multiplication
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A.47 × 8 ≡ 47 × 5 + 47 × 3 B.52 × 9 ≡ 30 × 9 + 20 × 9 + 2 × 9 C.87 × 8 ≡ 87 × 3.3 + 87 × 5.7 D.100 × 6 – 7 × 6 ≡ 93 × 6 E.49 × 7 ≡ 50 × 7 – 7 F.60 × 8 + 8 × 13 ≡ 73 × 8 True or False? ✓ ✗ ✓ ✓ ✓ ✓
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A.47 × 8 ≡ 47 × 5 + 47 × 3 So 47 × (5 + 3) ≡ 47 × 5 + 47 × 3 B.52 × 9 ≡ 30 × 9 + 20 × 9 + 2 × 9 So (30 + 20 + 2) × 9 ≡ 30 × 9 + 20 × 9 + 2 × 9 C.100 × 6 – 7 × 6 ≡ 93 × 6 100 × 6 – 7 × 6 ≡ (100 – 7) × 6 The Distributive Law of Multiplication
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We say that “multiplication is distributive over addition and subtraction”. A × B + A × C ≡ A × (B + C) A × (B – C) ≡ P × (Q + R – S) ≡ The Distributive Law of Multiplication
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51 × 8 + 51 × 14 ≡ 51 × 22 11 × 72 – 6 × 72 ≡ 72 × 17 58 × 19 + 58 × 11 – 58 × 5 ≡ 58 × 15 6.3 × 8 + 8 × 9.2 ≡ 6.3 × (8 + 9.2) 12 × 26 – 4 × 13 ≡ 13 × (24 – 4) 6.2 × 0.4 + 8 × 4 ≡ 4 × (6.2 + 8) True or False? ✗ ✓ ✓ ✗ ✗ ✗
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“Division is distributive over addition and subtraction”. Can you give a “number sentence” as an example of this? Can you give a “symbol sentence” as an example of this? Is your “symbol sentence” always, sometimes or never true? Convince yourself. Convince me! Agree or Challenge?
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