Everyday Mathematics Counting-Up Subtraction

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Everyday MathematicsCounting-Up Subtraction

Counting-Up SubtractionCounting-up subtraction involves:Subtracting by finding the distance between two numbers;Using benchmark numbers; andAdding smaller distances to get the final answer.

Everyday Mathematics

Counting-Up SubtractionSolve: 471 293We 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. Counting-Up SubtractionEveryday Mathematics

Solve: 471 293We first count up the distance fromthe starting number (293) to reachthe first benchmark number (300). That distance is 7.293+ 7300Counting-Up SubtractionEveryday Mathematics

Solve: 471 293From 300, our next benchmark number could be 400.So we count up the distance from 300 to 400.That distance is 100.

293+ 7300+ 100400Counting-Up SubtractionEveryday Mathematics

Solve: 471 293We can count up the distance from 400 to 471 in one step.

293+ 7300+ 100400+ 71 471Counting-Up SubtractionEveryday Mathematics

Solve: 471 293We circle all of the distances we counted up between the startingnumber (293) and the final number (471). Now we add the circled numbers.7 + 100 + 71 = 178

293+ 7300+ 100400+ 71 471Counting-Up SubtractionEveryday Mathematics

Solve: 471 293The distance between 293 and 471 is 178.This method is like counting up to make change.7+ 100+ 71178Counting-Up SubtractionEveryday Mathematics

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