# Accessible Algorithms For Subtraction - Subtraction Cheat Sheet

Level 2
(continued)
Accessible Algorithms for
Subtraction
Introduce the accessible algorithm presented below when
students learn about subtraction with regrouping. Support
students’ use of the algorithm whenever they are working on
subtraction that requires regrouping.
Ungroup First Method
Use with Houghton Mifflin Math, Ch 2, Lessons 3–4; Ch 11, Lesson 3.
This algorithm helps students to see the relationship between the
two numbers in subtraction. In the traditional, alternating
method of subtraction, students often view the two numbers as
columns of digits that are unrelated to each number as a whole.
By rewriting the top number so that it is ready for subtraction,
and then subtracting, students better understand the subtraction
process.
By ungrouping first where it is needed, students can work left-to-
right (as they read), or right-to-left. Students can be encouraged
to draw an oval "magnifying glass" around the top number
before they regroup. This helps students see that ungrouping
consists of breaking a number down into its parts to prepare it
for subtraction.
Subtract Multi-digit Numbers with Ungrouping
Left-to-Right
Right-to-Left
12
12
8
13
12
8
2
12
2,9
3
2
2,9
3
2
1,4 4 5
1,4 4 5
1,4 8 7
1,4 8 7
Less-advanced students may use the place-value meaning method,
pictured below, until they are ready to transition to the Ungroup
First Method.
1 2 0
8 0 0
1 3 0
1 2
2 , 9 3 2
2 , 0 0 0
9 0 0
3 0
2
1 , 4 4 5
1 , 0 0 0
4 0 0
4 0
5
1 , 4 8 7
1 , 0 0 0
4 0 0
8 0
7
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