Addition & Subtraction Strategies Explorer
Enter two numbers and switch between three visual strategies to understand how addition and subtraction work. See base-10 blocks combine or separate, watch hops on a number line, or follow the column method step by step. All computation runs in your browser.
Difficulty
Try an example
Result
34 + 25 = 59
Base-10 Blocks
Reference Guide
Regrouping in Addition
When digits in a column add to 10 or more, carry the extra ten to the next column.
This is called regrouping. Ten ones become one ten, and ten tens become one hundred.
Borrowing in Subtraction
When the top digit is smaller than the bottom digit, borrow 1 ten from the next column.
Borrowing is the reverse of carrying. One ten becomes ten ones so you have enough to subtract.
Number Line Strategy
Break the second number into friendly parts and hop along the number line.
This strategy makes mental math easier. Decompose into hundreds, tens, and ones, then add or subtract one part at a time.
Base-10 Blocks
Base-10 blocks use physical shapes to represent place value.
- Hundred flat = a 10 × 10 grid (100)
- Ten rod = a strip of 10 units (10)
- One cube = a single unit (1)
Ten ones regroup into one ten rod. Ten ten rods regroup into one hundred flat. This is how carrying and borrowing work with physical blocks.