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Maths

Written Addition with 3-Digit Numbers

Overview

Building on place value understanding, students learn to set out and solve column addition with 3-digit numbers, managing carrying systematically.

Learning Objective
Students use column addition to add two 3-digit numbers, including examples that require carrying (regrouping) into the next column.

Resources needed

  • Mini whiteboards or squared paper
  • Place value charts (optional)
  • Digit cards or base-ten blocks (optional)

Lesson stages

0 / 7 done
  1. 1 Write 347 on the board. 'What digit is in the hundreds place? Tens? Ones?' Quick fire for three numbers. Reinforce that position matters.
  2. 2 Model setting out 245 + 132 in columns. 'We line up hundreds with hundreds, tens with tens, ones with ones.' Stress the importance of alignment. 'This is why we use squared paper.'
  3. 3 Solve 245 + 132 together: ones first (5+2=7), tens (4+3=7), hundreds (2+1=3). Answer: 377. Demonstrate why we start with ones. Students practise two similar examples.
  4. 4 Set up 156 + 275. Ones: 6+5=11. '11 is 1 ten and 1 one — write the 1 in the ones column and carry the ten.' Show the small '1' written below the tens column. Tens: 5+7+1(carried)=13. Carry again. Hundreds: 1+2+1=4. Answer: 431.
  5. 5 Students solve three examples with carrying, guided by teacher. Write carrying digits small and clearly. Check each step before moving on.
  6. 6 Students solve 5 calculations independently, mixing carried and non-carried examples. Encourage checking by estimation first: '156 + 275 is roughly 160 + 280 = 440 — so about 430 seems right.'
  7. 7 Swap books with a partner and check each other's working. Discuss any differences. 'If you got different answers, work through it together.'

Tap a step to mark it as done.

Variations

  • Extend to 4-digit addition
  • Include money contexts (£2.45 + £1.32)
  • Add three 3-digit numbers in a column
More information

Display the terms: ones, tens, hundreds, carry, regroup. Say and write each step aloud: 'Six plus five equals eleven. I write one and carry one ten.'

Provide pre-ruled column grids for students who struggle with alignment. Use base-ten blocks to model carrying physically before recording.

Is the layout correctly aligned? Are carrying digits recorded clearly and in the right column? Do students add the carried digit consistently?

Draw column headings (H, T, O) on plain paper. Students create their own grid without squared paper.

Students carry the wrong digit (e.g. write 11 but carry 1 ten — they may write the ten and carry the one). Reinforce: write the units digit, carry the tens digit.

Activity details
Primary Medium 35 minutes 5 minutes prep Solo, Pairs Indoor
Topics
Addition Written Methods Place Value Regrouping