Unit 3: Subtraction                                                      subtraction

In this unit, the students will be encouraged to “brush up” on their basic subtraction facts, which they learned in second grade. Efficiency with basic facts, makes difficult subtraction problems more manageable. 

Subtraction vocabulary will be highlighted such as:

minuend- the first number in a subtraction sentence; the “whole amount”

subtrahend- the number to be subtracted

the difference- the answer to a subtraction problem (It’s the difference between the minuend and the subtrahend).

minus sign- a math symbol used to show subtraction

decrease- to get smaller

fewer- less

Various subtraction strategies will be taught for subtracting larger two and three digit numbers.  The “old school,” or standard algorithm, with and without regrouping (also know as “borrowing”) will be reviewed. The students will also be exposed to more modern approaches such as the use of an open number line, expanded form and mental math strategies. Estimating differences, balancing equations, and subtraction rules (in/out boxes) will also be covered in this unit.

Real world problems involving taking away, comparing (how many more/less), and missing information, will be utilized when practicing strategies for subtraction. The third graders have also learned how to use a “tape diagram” to represent part-part-whole and to assist with problem solving.

In addition, the mathematicians will explore the relationship between addition and subtraction, as well as the need for both operations when problem solving.