NumihanaA digit tells us how many of one place-value unit we have. In 243, the 2 means two hundreds, the 4 means four tens and the 3 means three ones. Column addition keeps those units together. Start by saying each number aloud, then put hundreds under hundreds, tens under tens and ones under ones.
Work through the example
- Write 243 above 125. The 3 and 5 share the ones column; the 4 and 2 share tens; the 2 and 1 share hundreds.
- Add the ones: 3 + 5 = 8 ones. Write 8 in the ones answer cell.
- Add the tens: 4 + 2 = 6 tens. Add the hundreds: 2 + 1 = 3 hundreds. The answer is 368.
- Check with the inverse: 368 − 125 = 243. Each column stays in the same place.
Why it works
Why start at ones when this example has no carrying? Using the same direction builds a routine for later examples where ten ones need to become one ten. Place-value headings are a support, not a substitute for understanding the size of each digit.
A common slip
Writing 125 one cell too far left changes it into a different amount. Point to the ones column in both rows before starting. Do not line up numbers by the left-hand edge.
For teachers & parents
Offer two-digit questions first if identifying hundreds is still difficult. Ask “What is the value of this 4?” rather than only asking for the digit name. Use counters or drawings to connect the written columns to quantities. Remove headings gradually when alignment is secure.
Talk it through
What would change if the bottom number were 152? Explain why 125 and 152 are different amounts, then predict which answer will be larger.
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