Line up the numbers with the larger one on top. Subtract column by column from the ones. When a top digit is too small, exchange one from the next place to the left.
Zeros need care. In 50 000 − 23 476, every place on top is 0 except the ten thousands. Exchange step by step: 5 ten thousands become 4 ten thousands and 10 thousands, and so on down to the ones. Check by adding your answer to the number you subtracted.
Worked example
Work out 63 205 − 28 718
- Ones: 15 − 8 = 7 after exchanging. Tens: 9 − 1 = 8 after exchanging. Hundreds: 11 − 7 = 4.
- Thousands: 12 − 8 = 4. Ten thousands: 5 − 2 = 3.
Answer:34 487
Key words
- exchange
- swap one bigger unit for ten smaller ones
- inverse
- addition undoes subtraction
- check
- add back to test the answer
Practise this
New questions every time.
Common Core-referenced: 4.NBT.B.4