Worked examples
Two examples
Example 1
15 − 8 =
- Count up from 8 to 15: 8 to 10 is 2, and 10 to 15 is 5.
- 2 + 5 = 7. Check: 8 + 7 = 15.
Answer: 7
Example 2
13 − 4 =
- Count up from 4: 4 to 10 is 6, and 10 to 13 is 3.
- 6 + 3 = 9. Check: 4 + 9 = 13.
Answer: 9
Where this is taught: Quiz 3: Addition and Subtraction with Regrouping, “Borrowing: trading down”
The drill
Ten problems
How many:
Type each answer, then press Check my answers at the bottom. Commas in large numbers are fine.Write each answer on the line. The answer key, with the reasoning, is on the last page.