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Concept Presentation Adding and Subtracting Negative Numbers. The Concept. A negative number is a number that is less than zero. It has the same magnitude but the opposite sign of its positive equivalent .
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The Concept A negative number is a number that is less than zero. It has the same magnitude but the opposite sign of its positive equivalent . The addition and subtraction of negative numbers is similar to the addition and subtraction of positive numbers, however, it can be problematic to some when considering taking away a negative number.
Why addition and subtraction of negative numbers? The Curriculum Rationale:‘Students should have the opportunity to understand and learn about… positive and negative numbers to at least seven digits’ (ECTL 16.EA.2) and ‘….compare and order sets of positive and negative numbers…’ (ECTL 16.EA.11)
Why addition and subtraction of negative numbers? Developmental Rationale: addition and subtraction of negative numbers enables students to practice their arithmetic skills and extend these into the negative domain. These skills are critical the comprehension of measurement systems and for graphing skills. Negative numbers are also required as the basis for complex number systems.
Why addition and subtraction of negative numbers? Societal Rationale: Negative numbers were first recognised by the Chinese around 100BC but were denied by Western cultures until the 17th Century
Why addition and subtraction of negative numbers? Practical Rationale: Negatives are required for: - Comprehension of change in direction or reduction of momentum in the positive direction (eg deceleration of a vehicle) - Understanding points below a reference (eg below sea level) - Comprehension of temperature - Understanding debt - Success in many computer games (eg Civilisation)
Concept 1: The Number Walk The concept is adapted from http://www.education.vic.gov.au/studentlearning/teachingresources/maths/mathscontinuum/number/N45003P.htm For this exercise you will need some willing volunteers and a number line, either made from paper or drawn on a footpath. For the worksheets you will require two dice and some coloured pencils.
Concept 2: Using coloured rods You will need about 20 coloured rods, blocks, post-it notes (or anything else you happen to have) per pair of students. You need 2 contrasting colours (1 for positive and 1 for negative) with 10 rods of each colour. Use the rods to complete various equations and problem solving activities (eg make -5 with 7 blocks or find how many ways there are to make -5)
