Written Addition of 3-digit Numbers with Regrouping

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1 Getting Started
2 Watch and Notice
3 Try It Together
4 Set Out the Sums in Your Copy
5 Class Challenge
Pupil practice

1 - Getting Started ~4 mins

Here is a question to start us off. If the units column in an addition comes to 13, that is more than nine ones. What should we do with the extra ten that does not fit in the units column?

Have a think, then we will look at the sum 156 + 138 together and decide where a trade is going to happen.

Teacher Notes

Take two or three hands-up answers, not open call-outs. Give five seconds of quiet think-time first.

You are listening for the idea that the extra ten moves left into the tens column. Write 156 + 138 on the board and ask pupils to point to the column where a trade will happen.

👇 Mark your steps as done as you complete them.

+5 XP

2 - Watch and Notice ~9 mins

The block pictures below show the final total after trading. We do the live trading together on the board first, then look at the finished blocks to check.

156 + 138

Before we add: which column do you think will trade? The units make fourteen, so we trade ten ones for one ten. We write the 4 in the units and the new ten joins the tens column.

247 + 185

Predict first: how many columns will trade this time? Two columns make ten or more, so we trade in the units and again in the tens. Watch the small carry written above each column.

308 + 196

Look hard at the zero in the tens column of 308. A trade still lands there. Tell me what you think happens to that empty column before we check.

475 + 268

This one is the hardest. Two trades happen one after the other. Watch how each carry is added in before we read the final answer.

Teacher Notes

Walk each example aloud, one at a time. These snapshots show the final total built in blocks; do the trading on a column-addition layout on the board first, then reveal the block total as the check.

Before each reveal, take two hands-up answers to the on-screen prediction so the watching stays active right across the beat.

156 + 138 = 294 — 6 + 8 makes fourteen; show ten ones traded for one ten and write the carry above the tens.
247 + 185 = 432 — two trades; pause on each carry.
308 + 196 = 504 — the trade lands on the empty tens column; say the zero is holding the place.
475 + 268 = 743 — two trades in a row; this is the hardest of the four.

👇 Mark your steps as done as you complete them.

+10 XP

3 - Try It Together ~9 mins

Now we work through these additions together on the board: build both numbers, then trade whenever a column makes ten or more.

We will go through four or five together — sums like 164 + 129, 273 + 158 and 345 + 286. Each pupil who comes up builds the two numbers and carries out the trade, and the rest of us say whether the carry is in the right place before we check.

Build and trade together

Teacher Notes

This round is for talking it through together — pupils take turns at the board and the class agrees or corrects out loud. Plan for four or five turns in the nine minutes.

Call a fresh 3-digit addition for each pupil (for example 164 + 129, 273 + 158, 345 + 286). Ask the class to predict which columns will trade before the pupil builds. Revoice a strong answer: so the ten ones become one ten, and the one ten moves left.

+15 XP

4 - Set Out the Sums in Your Copy ~3 mins

COPYBOOK MOMENT

In your maths copy, set out these two additions in columns, one under the other so the units, tens and hundreds line up:

264 + 158
437 + 295

Carry where a column makes ten or more, then read each answer aloud to yourself.

Teacher Notes

Walk the room glancing at column alignment and the position of each carry — this is whole-class copybook practice, not marking. The most common slip is a carry written in the wrong column or forgotten on the second trade.

+10 XP

5 - Class Challenge ~10 mins

Now we solve four real GAA-club problems, each one a little harder than the last:

A club sells 143 and 126 raffle tickets at two stalls. How many altogether?
A collection gathers 235 cans on Saturday and 187 on Sunday. How many in total?
Pupils take 318 steps to the pitch and 296 steps home on a sponsored walk. How many steps?
A hurling-skills stall stacks 467 cones in the morning and 358 in the afternoon. How many cones?

Key point

Add each one in your copy, then we check it together on the board.

Add the GAA totals

Teacher Notes

This round is the practice bank — pupils take turns at the board, check each answer, and the class confirms before moving on. Keep the board work brisk rather than over-explaining.

Answers: 269, 422, 614, 825. The cones problem (467 + 358) needs two trades — flag it as the toughest. As you call each one, ask which of these needs two trades?

+15 XP

Pupil practice

Module 2 · The Four Operations, Mental and Written Number

Lesson 15 · Written Addition of 3-digit Numbers with Regrouping

Download Activity Book page (PDF)

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Teacher Class Feed

1 - Getting Started ~4 mins

2 - Watch and Notice ~9 mins

156 + 138

247 + 185

308 + 196

475 + 268

3 - Try It Together ~9 mins

Build and trade together

4 - Set Out the Sums in Your Copy ~3 mins

5 - Class Challenge ~10 mins

Add the GAA totals

Unlock the full learning experience

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