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Subtraction

Level 30 / mastery

4d - 4d (mastery)

5 visual steps / borrow-window subtraction

1. Release thousands

1. Release thousandsRelease one digit; only borrow stays active.
answer strip
Pay right borrow; release 4: 9 - 4 - 1 = 4.

Pay right borrow; release 4: 9 - 4 - 1 = 4.

2. Release hundreds

2. Release hundredsRelease one digit; only borrow stays active.
answer strip
Borrow 10; pay right borrow: 10 - 6 - 1 = 3.

Borrow 10; pay right borrow: 10 - 6 - 1 = 3.

3. Release tens

3. Release tensRelease one digit; only borrow stays active.
answer strip
Borrow 10; pay right borrow: 10 - 8 - 1 = 1.

Borrow 10; pay right borrow: 10 - 8 - 1 = 1.

4. Release ones

4. Release onesRelease one digit; only borrow stays active.
answer strip
Borrow 10; release 8: 15 - 7 = 8.

Borrow 10; release 8: 15 - 7 = 8.

5. Read answer

5. Read answerRelease one digit; only borrow stays active.Read answerDrop finished digits; borrow is gone.
Read 4 | 3 | 1 | 8 as 4318; borrow is gone.

Read 4 | 3 | 1 | 8 as 4318; borrow is gone.

Practice Level 30

A few quick rounds make each dropped digit feel light; borrow is the only thing to keep.

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