Everyday Mathematics Counting-Up Subtraction

1. Everyday MathematicsCounting-Up Subtraction

2. Counting-Up Subtraction Counting-up subtraction involves: • Subtracting by finding the distance between two numbers; • Using benchmark numbers; and • Adding smaller distances to get the final answer. Everyday Mathematics

3. Counting-Up Subtraction Counting-Up Subtraction Solve: 471 – 293 We begin by thinking: • What is a good benchmark number to start with for this problem? Since we are finding the distance between 293 and 471, a first benchmark number could be 300. Everyday Mathematics

4. Counting-Up Subtraction Solve: 471 – 293 We first count up the distance from the starting number (293) to reach the first benchmark number (300). That distance is 7. 293 + 7 300 Everyday Mathematics

5. Counting-Up Subtraction Solve: 471 – 293 From 300, our next benchmark number could be 400. So we count up the distance from 300 to 400. That distance is 100. 293 + 7 300 + 100 400 Everyday Mathematics

6. Counting-Up Subtraction Solve: 471 – 293 We can count up the distance from 400 to 471 in one step. 293 + 7 300 + 100 400 + 71 471 Everyday Mathematics

7. Counting-Up Subtraction Solve: 471 – 293 We circle all of the distances we counted up between the starting number (293) and the final number (471). Now we add the circled numbers. 7 + 100 + 71 = 178 293 + 7 300 + 100 400 + 71 471 Everyday Mathematics

8. Counting-Up Subtraction Solve: 471 – 293 The distance between 293 and 471 is 178. This method is like counting up to make change. 7 + 100 + 71 178 Everyday Mathematics

9. Counting-Up Subtraction When children use counting-up subtraction, they practice a variety of skills related to number sense and algebraic reasoning. • Exploring the relationship between addition and subtraction; • Using benchmark numbers; and • Adding a set of distances to get a total. Many children find counting up much easier than taking away. For example: Everyday Mathematics