Topic D introduces formal subtraction concepts including writing and solving expressions and equations. Lesson 19 begins at the concrete level with students acting out take away stories and working at the pictorial level crossing off to see what remains. In Lesson 20, the concrete objects and pictorial representations are tied to or matched to the representative subtraction expression or equation using the minus sign with no unknown. As in Topic C, this progression helps students move from concrete processes to reasoning abstractly and quantitatively (MP.2). In Lesson 21, students solve subtraction story problems using concrete and pictorial representations and write the corresponding equation. As with addition, it is important that students understand what each numeral in the equation represents from the story situation. Lessons 22–24 focus on decompositions of 6, 7, and 8, which are recorded as equations. These equations are described in the progressions as take from with result unknown (C – B = ___) situations. These three lessons explore the decompositions of 6, 7, and 8 by breaking off a part, hiding a part, and crossing off a part. “There were 7 bears sleeping in a cave. Four bears left to go fishing. How many bears are still in the cave?”
Kindergarten Mathematics Module 4, Topic D
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Common Core Learning Standards
|K.OA.1||Represent addition and subtraction with objects, fingers, mental images, drawings2, sounds (e.g.,...|
|K.OA.2||Solve addition and subtraction word problems, and add and subtract within 10, e.g., by using...|
|K.OA.3||Decompose numbers less than or equal to 10 into pairs in more than one way, e.g., by using objects...|