CKMath Unit 2: Adding and Subtracting Within 100
Focus:
In this unit, students add and subtract within 100 using strategies based on place value, the properties of operations, and the relationship between addition and subtraction. Students begin by using any strategy to find the value of sums and differences that do not involve composing or decomposing a ten. They are then introduced to base-ten blocks as a tool to represent addition and subtraction and move towards strategies that involve composing and decomposing tens. Students develop their understanding of grouping by place value, and begin to subtract one- and two-digit numbers from two-digit numbers by decomposing a ten as needed. They apply properties of operations and practice reasoning flexibly as they arrange numbers to facilitate addition or subtraction. At the end of the unit, students apply their knowledge of addition and subtraction within 100 to solve one- and two-step story problems of all types, with unknowns in all positions. To support them in reasoning about place value when adding and subtracting, students may choose to use connecting cubes, base-ten blocks, tape diagrams, and other representations learned in earlier units and grades.
Number of Lessons: 16 and 4 optional
Instruction Time:
Approximately 60 minutes
(Please note that each lesson is designed for one instructional block, and may be divided into shorter or longer segments based on teacher pacing and student needs.)
Additional Search Terms:
place value • unknown addend • properties of operation • decompose • story problem
