Subtraction as Distance - Grades K-2

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Summary

We usually consider subtraction a “take-away” or “removal”, but what if we look at it as a distance? This view of subtraction promotes flexible thinking and provides another strategy for solving subtraction problems using a number line and is a critical precursor to the thinking required when students encounter integer subtraction and calculating distance on a coordinate grid.

Goals and Standards

Colorado Academic Standards:

1.OA.C.6. Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g.,8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 − 4 = 13 − 3 − 1 = 10 − 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 − 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).

Mathematical Practice Standards:

MP1. Make sense of problems and persevere in solving them.
MP7. Look for and make use of structure.

Learning Goal:

To extend the understanding of subtraction to include distance between two numbers.
Communicate verbally how a strategy is used to solve a subtraction problem.