Forgetting the carry explained

Homework shows 47 + 28 in columns. Your child adds the ones - 7 + 8 = 15 - writes 5, and somehow the tens become 6 instead of 7. The missing 1 (the renamed ten) never made it next door. Parents call that forgetting the carry. Australian classrooms often say regrouping, renaming or trading. Same bug, different words.

This guide zooms into that sticky moment: why children drop the ten, how expanded form makes the rename visible before columns, and calm home games. It is not a full tour of joining strategies. For part–part–whole, counting on and make-ten, see addition explained. Strong place value is the floor under every rename — including why zero holds the place in numbers like 1005. A quick estimate before you add often catches a dropped ten before the sheet goes in.

Carry, regroup, rename: same idea

Parents grew up writing a tiny 1 above the tens column. Many Australian teachers prefer language that describes what the digits mean:

• Regrouping / renaming / trading: ten ones become one ten (or ten tens become one hundred).
• Carrying: the everyday shorthand for recording that renamed ten in the next column.

Match the teacher's word at home. The maths underneath is place value: fifteen ones really are 1 ten and 5 ones - not "fifteen stuck in the ones place".

Australian Curriculum Mathematics (version 9) builds addition with place value into written methods through the primary years (Foundation–Year 4). At home: "When this column hits ten or more, rename and move the extra ten next door."

Why kids drop the ten

Working memory overload. Column addition asks children to add, decide whether to rename, write the ones digit, and remember the renamed ten. Something drops. The ones digit usually survives; the renamed ten is the orphan.

"Write 5" without saying the full rename. They know 7 + 8 = 15, jot 5, and move on - the "1 ten" never gets spoken or marked. Fix: insist on the full sentence out loud: "Fifteen ones is one ten and five ones."

Place-value wobble. If tens and ones still feel like separate digits rather than sizes, renaming is magic, not sense. Rebuild with materials before more columns - see place value explained.

Rushing the tens. Ones done, they add the tens digits they see (4 + 2) and skip the tiny carry mark. Fix: point to the renamed ten every time before the tens add starts.

No reasonableness check. An answer of 65 for 47 + 28 can feel "fine" if nobody asked "about how many?" first. A ballpark near 80 (from estimate before you add) makes 65 look suspicious.

Jumping to columns too early. If mental strategies and tens/ones are shaky, columns amplify mistakes. Make ten bridging and number bonds still matter beside written methods.

If the wobble sits inside a wider "are they behind?" worry, see Is my child behind in maths?.

Expanded form first, then the column

Before neat vertical sums, show the same addition expanded:

47 + 28

• 47 = 40 + 7
• 28 = 20 + 8
• Ones: 7 + 8 = 15 = 10 + 5
• Tens: 40 + 20 + 10 (from the ones) = 70
• Total: 70 + 5 = 75

Now the "carry" is not a mysterious floating 1 - it is the 10 from renaming fifteen ones. Base-ten blocks, bundled icy-pole sticks or sticks-and-dots drawings make that trade visible.

Same sum in columns (say it as you write): ones 7 + 8 = 15 → write 5, rename 1 ten into the tens; tens 4 + 2 + 1 = 7. Answer: 75.

Practise expanded then column on the same numbers until the rename sentence is automatic. This page owns the repair when the renamed ten keeps disappearing.

Year by year: where columns and renaming show up

Year 2 - tens and ones, informal jotting, early written addition; renaming may begin once place value is steady (Year 2 maths).

Year 3 - larger numbers and clearer written methods; forgetting the renamed ten becomes a common homework pattern (Year 3 maths).

Year 4 - multi-digit consolidation, money and measurement contexts; reasonableness checks help catch dropped renames (Year 4 maths).

The reverse rename (borrowing a ten when a column is short) appears in subtraction explained - same place-value idea, opposite direction.

Worked examples you can say aloud

Classic drop. 36 + 47. Ones: 6 + 7 = 13 → write 3, rename 1 ten. Tens: 3 + 4 + 1 = 8. Answer 83. The bug version writes 3 then 3 + 4 = 7 → 73.

Two renames. 58 + 67. Ones: 15 → write 5, rename 1 ten. Tens: 5 + 6 + 1 = 12 → write 2, rename 1 hundred → 125. Dropping the ones→tens rename often lands on 115.

No rename needed. 41 + 25 → 66. Practise a no-rename sum beside a rename sum so children notice when the move is required.

Estimate first. 47 + 28 → about 50 + 30 = 80. Exact 75 sits near 80; 65 (dropped ten) does not. Pair columns with estimate before you add.

Common mix-ups (and kinder fixes)

Writing 15 in the ones place. Fix: only one digit lives in ones - the leftover ones; the ten moves next door.

Carry mark in the wrong column. Fix: "The renamed ten sits above the tens."

Adding the carry as ones. Fix: say "one ten", not "plus one".

Only renaming when both ones look "big". Fix: any ones sum of 10 or more renames - including 9 + 1.

Skipping materials. Fix: one rename with sticks or a drawing before the pencil version each session.

Tears over columns. Shrink the sheet; one carefully spoken rename beats five rushed ones - see homework without tears and maths anxiety in primary kids.

Home games that do not feel like worksheets

Stick bundle rename. Make 7 sticks + 8 sticks. Bundle ten into a new ten-stick; five left. Say "one ten and five ones" before writing anything.

Expanded on scrap paper. Write 40 + 7 and 20 + 8; circle the ones; rename; combine tens. Then copy into a column.

"Did we rename?" checkpoint. After every column sum, tick yes/no. If yes, point to the carry mark and re-add the tens including it.

Estimate then column. Whisper a friendly ballpark; do the column; compare. Catches many dropped tens without nagging.

Money total. Two prices that force a rename (e.g. $1.70 + $0.85) - same place-value story in everyday joins; see money maths at home.

Keep each activity under ten minutes. Tell the teacher the exact collapse ("skips the renamed ten") so class and home use one phrase.

A simple weekly home routine

1. Two minutes of rename talk - "Fifteen ones is one ten and five ones" with sticks or fingers.
2. Five minutes of one column sum - expanded form first if last week's carry vanished; then the vertical layout.
3. Three minutes of a check - estimate ballpark, or add the tens again while pointing at the carry mark.

How this links to other guides

• Addition explained - full joining progression; this page owns the dropped-rename repair
• Place value explained - tens and ones under every regroup
• Make ten bridging - mental bridge-to-ten that still helps before columns
• Estimate before you add - reasonableness catch for missing tens
• Number bonds explained - pairs to 10 that make "how many to rename?" easier
• Subtraction explained - renaming in the opposite direction
• Year 2–Year 4 maths year maps - where written addition sits

Ask the teacher: "What word do you use - carry, regroup, rename or trade - and do you want expanded form before columns when the renamed ten keeps disappearing?"

FAQ

Is carrying wrong if the school says renaming?

No. Carrying is the recording habit; renaming describes the place-value idea. Echo the class term so homework and school match.

My child "gets" 7 + 8 = 15 but still drops the ten. Why?

Knowing the fact is not the same as recording the rename. Practise the full sentence and a visible mark above the tens every time.

Should we ban columns until place value is perfect?

Not forever - but if renames keep vanishing, pause for materials and expanded form, then return to one careful column. See place value explained.

How is this different from addition explained?

Addition explained covers the whole joining toolkit. This page is the forgetting-the-carry deep dive: language, why the ten drops, expanded-then-column repair, and home games for that bug. Distinct from split-add-join (partition then add) - here the focus is the written rename in columns.

Do we need special kits?

No. Sticks, pasta, scrap paper and a pencil are enough.

A calm next step

When the rename sentence and one careful column feel steadier and you want a wider number-skill snapshot at home, Ziado's free check is a one-off, roughly 10-minute adaptive diagnostic with partial results only - no account and no card. The full placement unlocks after signup. It is not NAPLAN practice and it is not the full product; Ziado's ongoing path is adaptive maths (Foundation–Year 6) plus phonics reading (Foundation–Year 4). Explore Ziado maths if you want practice that can meet place-value and addition skills at the right step. Individual and Family plans, if you continue later, start with a 14-day free trial of the full app — see pricing for current plans.

The reverse rename (trading a ten when a column is short) is covered in regrouping in subtraction explained.

Split-add-join partitions then joins (not a written carry) — see split add join explained.