Regrouping Regrouping for for

Double-Digit Double-Digit SubtractionSubtraction

Two-Digit Subtraction – Regrouping

Two approaches:Two approaches:

Two-Digit Subtraction – Regrouping

““10 First” Approach10 First” Approach

Common ApproachCommon Approach

1. “10 First” Approach1. “10 First” Approach

Two-Digit Subtraction – Regrouping

66

2323--1616

Start with subtracting the units columnStart with subtracting the units column

Two-Digit Subtraction – Regrouping

2323--1616

33 66

First, put 3 on Mathline First, put 3 on Mathline

Two-Digit Subtraction – Regrouping

2233--1616

Can we subtract six?Can we subtract six?

Two-Digit Subtraction – Regrouping

2323--1616

66

2233--1616

66

No, 3 is less than 6No, 3 is less than 6

Two-Digit Subtraction – Regrouping

So we need to regroupSo we need to regroup

2323--1616

66

10 First Approach!10 First Approach!

Two-Digit Subtraction – Regrouping

2323--1616

66

Start by clearing the Start by clearing the MathLineMathLine

Two-Digit Subtraction – Regrouping

2323--1616

66

Count 10 from right and Count 10 from right and move overmove over

Two-Digit Subtraction – Regrouping

2323--1616

66

This is regroupingThis is regrouping

Two-Digit Subtraction – Regrouping

1 1

One ten becomes ten onesOne ten becomes ten ones

2233--1616

66

Now put the 3 ones backNow put the 3 ones back

Two-Digit Subtraction – Regrouping

1 1

2323--1616

66

Now put the 3 ones backNow put the 3 ones back

Two-Digit Subtraction – Regrouping

1 133 66

2323--1616

66

Two-Digit Subtraction – Regrouping

1 133 66

See 13See 13

2323--1616

66

Now take 13 minus 6Now take 13 minus 6

Two-Digit Subtraction – Regrouping

1 133 66

123456

2323--1616

66

See 7See 7

Two-Digit Subtraction – Regrouping

1 133 6677

Now we clear the MathLine

to subtract the tens column

Two-Digit Subtraction – Regrouping

2323--1166

1

77

1

Count ten rings on MathLine

Two-Digit Subtraction – Regrouping

2323--1616 7

11

77

Two-Digit Subtraction – Regrouping

2323--1166 7

11

77Then subtract 10

Count ten rings on MathLine

Two-Digit Subtraction – Regrouping

2323--1166 7

11

77

See zero on MathLine

00

2. Common Approach2. Common Approach

Two-Digit Subtraction – Regrouping

66

2323--1616

Start with subtracting the units columnStart with subtracting the units column

Two-Digit Subtraction – Regrouping

2323--1616

33 66

First, put 3 on Mathline First, put 3 on Mathline

Two-Digit Subtraction – Regrouping

2233--1616

Can we subtract six?Can we subtract six?

Two-Digit Subtraction – Regrouping

2323--1616

66

2233--1616

66

No, 3 is less than 6No, 3 is less than 6

Two-Digit Subtraction – Regrouping

So we need to regroupSo we need to regroup

2233--1616

66

Common Approach!Common Approach!

Two-Digit Subtraction – Regrouping

2323--1616

Count 10 rings from Count 10 rings from the right side to regroup.the right side to regroup.

Two-Digit Subtraction – Regrouping

1

2323--1616

Two-Digit Subtraction – Regrouping

1 2

Count 10 rings from Count 10 rings from the right side to regroup.the right side to regroup.

2323--1616

Two-Digit Subtraction – Regrouping

Count 10 rings from Count 10 rings from the right side to regroup.the right side to regroup.

1 2 3

2323--1616

Two-Digit Subtraction – Regrouping

Count 10 rings from Count 10 rings from the right side to regroup.the right side to regroup.

2 31 4

2323--1616

Two-Digit Subtraction – Regrouping

Count 10 rings from Count 10 rings from the right side to regroup.the right side to regroup.

2 31 4 5

2323--1616

Two-Digit Subtraction – Regrouping

Count 10 rings from Count 10 rings from the right side to regroup.the right side to regroup.

2 31 4 5 6

2323--1616

Two-Digit Subtraction – Regrouping

Count 10 rings from Count 10 rings from the right side to regroup.the right side to regroup.

2 31 4 5 6 7

2323--1616

Two-Digit Subtraction – Regrouping

Count 10 rings from Count 10 rings from the right side to regroup.the right side to regroup.

2 31 4 5 6 7 8

2323--1616

Two-Digit Subtraction – Regrouping

Count 10 rings from Count 10 rings from the right side to regroup.the right side to regroup.

2 31 4 5 6 7 8 9

2323--1616

Two-Digit Subtraction – Regrouping

Count 10 rings from Count 10 rings from the right side to regroup.the right side to regroup.

2 31 4 5 6 7 8 9 10

2323--1616

66

Explain this ten came Explain this ten came from the tens column from the tens column

1 1

Two-Digit Subtraction – Regrouping

Move rings to the left. Move rings to the left.

This is regrouping! This is regrouping!

2233--1616

Two-Digit Subtraction – Regrouping

2233--1166

1 1Next, subtract 13 minus 6 Next, subtract 13 minus 6

123456

1

Two-Digit Subtraction – Regrouping

2323--1616

1 1

See 7 in the ones columnSee 7 in the ones column

77

1

Now we clear the MathLine

to subtract the tens column

Two-Digit Subtraction – Regrouping

2323--1166

1

77

1

Count ten rings on MathLine

Two-Digit Subtraction – Regrouping

2323--1616 7

11

77

Two-Digit Subtraction – Regrouping

2323--1166 7

11

77Then subtract 10

Count ten rings on MathLine

Two-Digit Subtraction – Regrouping

2323--1166 7

11

77

See zero on MathLine

00