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3 Models for Subtraction Algorithms

3 Models for Subtraction Algorithms. By Kim Iverson. Subtraction. Subtraction is usually explained as the taking away of a subset of objects from a given set. . Subtraction.

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3 Models for Subtraction Algorithms

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  1. 3 Models for Subtraction Algorithms By Kim Iverson

  2. Subtraction Subtraction is usually explained as the taking away of a subset of objects from a given set.

  3. Subtraction The process of taking away, or subtraction, may be thought of as the opposite of the process of putting together, or addition. Because of this double relationship, subtraction and addition are called inverse operations. This connection is used to define subtraction in terms of addition.

  4. Algorithm An algorithm is a step-by-step procedure for computing.

  5. 3 MODELS FOR SUBTRACTION ALGORITHMS 1. Take-Away Concept 2. Comparison Concept 3. Missing Addend Concept

  6. Take-Away Concept EXAMPLE: Suppose that you have 9 stars and give away 6. How many stars will you have left?

  7. Lets break the problem down We have a total of 9 stars.

  8. Take-Away Concept We are giving 6 stars away. We can represent these 6 stars by changing their color to red

  9. Take-Away Concept Once we take these 6 red stars away, we are left with 3 blue stars. Therefore: 9-6=3

  10. Comparison Concept EXAMPLE: Suppose that you have 9 frogs and someone else has 6 frogs. How many more frogs do you have than the other person? In this case we compare one collection to another to determine the difference.

  11. Comparison Concept We know that the first person has a total of 9 frogs.

  12. Comparison Concept We know that the second person has 6 frogs. We can line up the amounts of frogs each person has to obtain our answer.

  13. Comparison Concept We can see that there are 3 frogs that do not match up with one another. Therefore: 9-6=3

  14. Missing Addend Concept Suppose that you have 6 pigs and you need to have a total of 9 pigs. How many more pigs are needed? In this case we can count up from 6 to 9 to determine the missing addend.

  15. Missing Addend Concept We start with 6 pigs.

  16. Missing Addend Concept We know that we need a total of 9 pigs. + ? =

  17. Missing Addend Concept We need to add 3 pigs to the 6 pigs to get a total of 9 pigs. Therefore: 9-6=3 + =

  18. Practice Worksheet 3 Models for Subtraction Algorithms Worksheet http://ellerbruch.nmu.edu/classes/cs255f04/cs255students/kiverson/p13/worksheet.pdf Students can either read over the worksheet and follow the directions and complete on a separate piece of paper or they can print out the worksheet and complete it. Make sure to read the directions carefully and show all work. 3 Models for Subtraction Algorithms Worksheet Answers http://ellerbruch.nmu.edu/classes/cs255f04/cs255students/kiverson/p13/worksheetanswers.pdf The answers to the worksheet are shown here.

  19. Game Take It Away http://www.primarygames.com/takeaway/question%201.htm This is a simple subtraction game for students to play. Students should have no problems with computing the answers. Students are to take the problems from the game, write them down on a sheet of paper and then tell what method they used to solve the problem and explain the steps they took. The actually working out of the problem and understanding the difference in the methods is the main objective here.

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