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How might we represent 3 + 6.5 + 7 + 11.5 in a different way?
Learning Target:Students will learn how to calculate decimal numbers by adding and subtracting.  Students will learn the communicative and associative properties of addition.
BIG IDEAS:MUST LINE UP YOUR DECIMALSADD ZEROS WHERE NECESSARYBRING DECIMAL STRAIGHT DOWN ADD OR SUBTRACT LIKE NORMAL
Find the sum or difference.3.286 + 4.5115 – 2.08
Answers:  3.286+4.510 7.79615.00-  2.0812.92
Evaluate the expression when x = 5.82 and y = 9.1.4.7 + xy – x
Answers:   4.70+ 5.82 10.52  9.10- 5.82 3.28
Properties of Addition:Commutative Property – You can add numbers in any order.2 + 4 = 4 + 2a + b = b + aAssociative Property – The value of a sum does not depend on how the numbers are grouped.(2 + 4) + 5 = 2 + (4 + 5)(a + b) + c = a + (b + c)
Tell which property is being illustrated. Then use mental math to evaluate the expression in red.(6.4 + 4.8) + 5.2 = 6.4 + (4.8 + 5.2) 9.3 + 2.9 = 2.9 + 9.3
Answers:(6.4 + 4.8) + 5.2 = 6.4 + (4.8 + 5.2)Associative Property(the groupings changed)16.49.3 + 2.9 = 2.9 + 9.3Commutative Property(the order changed)12.2
1st person: Find the total cost for a pair of headphones that costs $19.75, two CDs that cost $11.50 each and a pack of batteries that costs $4.25.2nd person: Find the total cost for two notebooks that cost $1.45 each, two pads that cost $0.55 each and one box of pencils that cost $2.75.Share your answer with the other person
Answers:Total cost of the CDs, head phones and batteries is $47.00.Total cost for the box of pencils, 2 pads of paper and 2 notebooks is $6.75.
Can you calculate decimal numbers by adding and subtracting?

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Section 3.6

  • 1. How might we represent 3 + 6.5 + 7 + 11.5 in a different way?
  • 2. Learning Target:Students will learn how to calculate decimal numbers by adding and subtracting. Students will learn the communicative and associative properties of addition.
  • 3. BIG IDEAS:MUST LINE UP YOUR DECIMALSADD ZEROS WHERE NECESSARYBRING DECIMAL STRAIGHT DOWN ADD OR SUBTRACT LIKE NORMAL
  • 4. Find the sum or difference.3.286 + 4.5115 – 2.08
  • 5. Answers: 3.286+4.510 7.79615.00- 2.0812.92
  • 6. Evaluate the expression when x = 5.82 and y = 9.1.4.7 + xy – x
  • 7. Answers: 4.70+ 5.82 10.52 9.10- 5.82 3.28
  • 8. Properties of Addition:Commutative Property – You can add numbers in any order.2 + 4 = 4 + 2a + b = b + aAssociative Property – The value of a sum does not depend on how the numbers are grouped.(2 + 4) + 5 = 2 + (4 + 5)(a + b) + c = a + (b + c)
  • 9. Tell which property is being illustrated. Then use mental math to evaluate the expression in red.(6.4 + 4.8) + 5.2 = 6.4 + (4.8 + 5.2) 9.3 + 2.9 = 2.9 + 9.3
  • 10. Answers:(6.4 + 4.8) + 5.2 = 6.4 + (4.8 + 5.2)Associative Property(the groupings changed)16.49.3 + 2.9 = 2.9 + 9.3Commutative Property(the order changed)12.2
  • 11. 1st person: Find the total cost for a pair of headphones that costs $19.75, two CDs that cost $11.50 each and a pack of batteries that costs $4.25.2nd person: Find the total cost for two notebooks that cost $1.45 each, two pads that cost $0.55 each and one box of pencils that cost $2.75.Share your answer with the other person
  • 12. Answers:Total cost of the CDs, head phones and batteries is $47.00.Total cost for the box of pencils, 2 pads of paper and 2 notebooks is $6.75.
  • 13. Can you calculate decimal numbers by adding and subtracting?