lesson
Keep the places lined up
1 · Learn
Write ones under ones, tens under tens and so on. In addition, exchange ten of one unit for one of the next. In subtraction, exchange a larger unit when a smaller column has too few units.
For 2,768 + 1,457, the ones total 15. Record 5 ones and carry a ten. The tens total 12 including that ten; the hundreds then total 12 including the new hundred.
2 · Worked example
For 5,032 − 1,786, exchanges give 4 thousands, 9 hundreds, 12 tens and 12 ones before subtraction. The result is 3,246.
3 · Your turn
Calculate 3,485 + 2,736 and 6,004 − 2,578. Check one answer with the inverse.
Check your answer
6,221 and 3,426. For example, 3,426 + 2,578 = 6,004.
4 · Apply your learning
Draw the exchanges for the subtraction before recording a formal column method. Estimate each answer first.
Adult guidance and safety
Use practical or drawn representations and explain the method. Check units and labels. A correct answer to one example is not evidence of secure fluency; revisit with varied numbers and feedback.
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