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Published byOtakar Bednář Modified over 5 years ago
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Today we will understand how to add and subtract negative numbers
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Hole in the sand Sandcastle -1 +1 or 1 = 0 -1 + (+1) = 0 = 0 +1 + (-1) = 0
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Adding -2 + -4 = - 6
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3 + -3 = 0
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= 2
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= -1
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Draw diagrams to explain your answers to these questions
(-5) = 2 = 2 7 (-5) = 1 6 = -1 = -2 -6 = -3 4 (-4 ) = -3 8
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How many ways can you fill the boxes?
Challenge: How many ways can you fill the boxes? Make one box positive and one box negative = -1 What happens to the answer if you increase the number of sandcastles and holes in the boxes by 1? Why is this?
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5 - 2 5 - 2 = 3
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-7 - (- 4) -7 - (- 4) = -3
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Notice anything interesting?
= -3 Notice anything interesting? Subtracting -4 is the same as adding 4.
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Notice anything interesting?
= -3 Notice anything interesting? Does subtracting -3 give the same answer as adding 3
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-10 – (-3) = -7 -7 =
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How can you take away 4 holes that aren’t there???
6 – (- 4) = 10 What addition would give you the same answer? Why? 6 – (-4) = 6 + 4 = 10
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8 – (- 5) 8 + 5 = 13 -6 – (-2) -6 + 2 = - 4 8 + 10 8 – (-10 ) = 18
For each question write the alternative calculation 8 – (- 5) 8 + 5 = 13 -6 – (-2) -6 + 2 = - 4 8 + 10 8 – (-10 ) = 18
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Use diagrams to explain your answers
= 6 (-2) = 10 = -10 (-2 )= -6 3. 2 – 8 = -6 7. -2 – (-8) = 6 4. -2 – 8 = -10 8. 2 – (-8) = 10 Why do 2 and 4 give the same answer, but not 1 and 3?
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