Subtraction within 20: A Range of Strategies for Solving 14-8
By Cindy Aossey (KCM) and Funda Gonulates (NKU)
Developing flexible subtraction strategies depends on flexibly navigating two different interpretations of subtraction:
- take-away - subtraction as items removed
- distance apart - connect to addition with an unknown addend, find the difference between the numbers
In this video, we explore a range of strategies for 14-8, including counting back in chunks, compensation, relating to a double, and think addition. We also show how a teacher might record a student's thinking on a bar model, an empty number line, and with symbolic notation, while connecting their reasoning to a concrete manipulative such as unifix cubes or to a story context. Through these kinds of discussions, students learn to use the relationship between addition and subtraction, strategically decompose and adjust quantities, and build a foundation for efficient and flexible mental computation.
Targeted Standards: KY.1.OA.3, KY.1.OA.4, KY.1.OA.5, KY.1.OA.6, KY.2.OA.2