Addition with carrying
- Input
- 456 + 789
- Expected output
- 1245
Carrying in three columns in a row.
Carregando ferramenta… / Loading tool…
column subtraction with borrowing
In a column calculation, digits line up by place: ones under ones, tens under tens. Addition goes from right to left with carrying, and subtraction with borrowing when the top digit is smaller. The Work it out tab opens on the subtraction 1,002 − 457, the hardest kind, with chained zeros.
Carrying in three columns in a row.
Fill 5.5 with a zero: 5.50.
One borrow, from the tens to the ones.
Chained borrow passing through two zeros.
The problem worked is 52 − 27 and the result takes a minus sign.
Start with the easy ones (1, 2, 5, 10), then use the rule that order does not matter: if you know 3 × 7 you already know 7 × 3. That leaves 36 distinct products between 2 and 9. Practice a few at a time, in short sessions of 10 to 20 facts, and let Practice repeat the ones you miss: it gives them more weight when drawing.
It is the tens digit of a column sum that goes past 9. In 6 + 9 = 15 you write the 5 and carry the 1 to add in the next column.
Borrow from the first nonzero digit to the left. Every zero on the way becomes 9, and the digit that needed it becomes 10 plus itself. In 1,000 − 1, the result is 999.
Each operation undoes the other. To check an addition, subtract one addend from the total. To check a subtraction, add the result to the subtrahend and see whether you get back to the minuend.
Your practice progress stays in this browser only. Nothing is sent to any server.
Related: Fraction calculator · Divisors of a number · GCD and LCM