Transcript Two approaches

Two-Digit Subtraction – Regrouping
Regrouping
for
Double-Digit
Subtraction
Two-Digit Subtraction – Regrouping
Two approaches:
“10 First” Approach
Common Approach
Two-Digit Subtraction – Regrouping
1. “10 First” Approach
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Two-Digit Subtraction – Regrouping
Start with subtracting the units column
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6
Two-Digit Subtraction – Regrouping
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First, put 3 on Mathline
Two-Digit Subtraction – Regrouping
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6
Can we subtract six?
Two-Digit Subtraction – Regrouping
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6
No, 3 is less than 6
So we need to regroup
Two-Digit Subtraction – Regrouping
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10 First Approach!
Two-Digit Subtraction – Regrouping
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Start by clearing the
MathLine
Two-Digit Subtraction – Regrouping
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Count 10 from right and
move over
Two-Digit Subtraction – Regrouping
1 1
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This is regrouping
One ten becomes ten ones
Two-Digit Subtraction – Regrouping
1 1
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Now put the 3 ones back
Two-Digit Subtraction – Regrouping
1 1
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Now put the 3 ones back
Two-Digit Subtraction – Regrouping
1 1
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See 13
Two-Digit Subtraction – Regrouping
1 1
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3
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Now take 13 minus 6
6 5 4 3 2 1
Two-Digit Subtraction – Regrouping
1 1
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7
See 7
Two-Digit Subtraction – Regrouping
1 1
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7
Now we clear the MathLine
to subtract the tens column
Two-Digit Subtraction – Regrouping
1 1
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Count ten rings on
MathLine
Two-Digit Subtraction – Regrouping
1 1
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Count ten rings on
MathLine
Then subtract 10
Two-Digit Subtraction – Regrouping
1 1
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See zero on MathLine
Two-Digit Subtraction – Regrouping
2. Common Approach
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6
Two-Digit Subtraction – Regrouping
Start with subtracting the units column
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3
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6
Two-Digit Subtraction – Regrouping
23
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First, put 3 on Mathline
Two-Digit Subtraction – Regrouping
23
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6
Can we subtract six?
Two-Digit Subtraction – Regrouping
23
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6
No, 3 is less than 6
So we need to regroup
Two-Digit Subtraction – Regrouping
23
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6
Common Approach!
Two-Digit Subtraction – Regrouping
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Count 10 rings from
the right side to regroup.
1
Two-Digit Subtraction – Regrouping
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Count 10 rings from
the right side to regroup.
12
Two-Digit Subtraction – Regrouping
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Count 10 rings from
the right side to regroup.
12 3
Two-Digit Subtraction – Regrouping
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Count 10 rings from
the right side to regroup.
12 3 4
Two-Digit Subtraction – Regrouping
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Count 10 rings from
the right side to regroup.
12 3 4 5
Two-Digit Subtraction – Regrouping
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Count 10 rings from
the right side to regroup.
12 3 4 5 6
Two-Digit Subtraction – Regrouping
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Count 10 rings from
the right side to regroup.
12 3 4 5 6 7
Two-Digit Subtraction – Regrouping
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Count 10 rings from
the right side to regroup.
12 3 4 5 67 8
Two-Digit Subtraction – Regrouping
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Count 10 rings from
the right side to regroup.
12 3 4 5 67 89
Two-Digit Subtraction – Regrouping
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Count 10 rings from
the right side to regroup.
1 2 3 4 5 6 7 8 9 10
Two-Digit Subtraction – Regrouping
1 1
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Explain this ten came
from the tens column
Move rings to the left.
This is regrouping!
Two-Digit Subtraction – Regrouping
1 1
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Next, subtract 13 minus 6
6 5 4 3 2 1
Two-Digit Subtraction – Regrouping
1 1
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7
See 7 in the ones column
Two-Digit Subtraction – Regrouping
1 1
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7
Now we clear the MathLine
to subtract the tens column
Two-Digit Subtraction – Regrouping
1 1
23
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7
Count ten rings on
MathLine
Two-Digit Subtraction – Regrouping
1 1
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7
Count ten rings on
MathLine
Then subtract 10
Two-Digit Subtraction – Regrouping
1 1
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07
See zero on MathLine