Adding Decimals: Line up the Points

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1 Getting Started
2 Watch and Notice
3 Try It Together
4 Set up Each Sum in Your Copy
5 Class Challenge
6 What Did We Notice?
7 What's Next
Pupil practice

1 - Getting Started ~5 mins

Illustration for Getting Started Here is a sum written out for adding: 4.7 + 0.85. But look closely at the way it is set up. Is this layout right? What looks wrong about how the two numbers are lined up?

Teacher Notes

Write 4.7 + 0.85 on the board stacked so the right-hand edges line up (so the 7 sits over the 5). Take three hands-up answers, not open call-outs. Listen for a pupil noticing the points don't match up. Don't fix it yet — that is the whole job of Watch and Notice.

👇 Mark your steps as done as you complete them.

+5 XP

2 - Watch and Notice ~11 mins

Illustration for Watch and Notice

4.7 + 0.85 = 5.55

Watch as we line up the decimal points one under the other. Lining up the points keeps tenths above tenths and hundredths above hundredths, so each column adds like-for-like. Once the points match, we can fill the empty hundredths place on 4.7 with a zero to make 4.70. Now every column has a digit to add.

0.3 + 0.27 = 0.57

Watch this one. The points line up, and 0.3 becomes 0.30 so there is a digit in the hundredths column.

9.99 + 0.01 = 10.00

This one is special. When we add the hundredths we get ten, so it regroups. Then the tenths regroup, then the units. Watch how the whole thing builds up to a clean ten.

Teacher Notes

Walk each example aloud, one at a time.

4.7 + 0.85 — point at the decimal points first and say 'points under points', then drop the trailing zero into the empty hundredths place.
0.3 + 0.27 — same trailing-zero move; ask the class where the zero goes before you show it.
9.99 + 0.01 — pause on the cascade of carries; ask 'what comes next?' before each column regroups.

The trailing zero is the make-or-break move — keep coming back to it.

👇 Mark your steps as done as you complete them.

+10 XP

3 - Try It Together ~10 mins

Today we work through these sums together: 1.05 + 2.34, then 0.6 + 0.27, then 4.8 + 3.65. For each one we will line up the decimal points first, add a trailing zero where a column is empty, then work each column from the right.

Add the decimals 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.

Let an individual pupil set each addend into the column-addition activity and step the columns. Before each column lands, ask the class to predict any carry. The 0.6 + 0.27 example has the lonely hundredth — watch pupils want to ignore the empty hundredths place; insist that 0.6 gets a placeholder zero (making 0.60). Revoice a good answer: 'so the point keeps everything lined up, and the empty place just gets a zero.'

+15 XP

4 - Set up Each Sum in Your Copy ~5 mins

COPYBOOK MOMENT

Illustration for Set Up Each Sum in Your Copy In your maths copy, set up each decimal sum vertically with the decimal points lined up one under the other. Add a trailing zero to fill any empty column. Work each column with the class, and write the answer with its decimal point in the right place.

4.7 + 0.85
0.3 + 0.27
1.05 + 2.34

Teacher Notes

Walk the room glancing at whether the decimal points sit in a straight vertical line and whether the trailing zeros have gone in. No marking — this is whole-class copybook practice, not assessment.

+10 XP

5 - Class Challenge ~11 mins

Now we work through a short ladder of decimal sums together, each one a little harder than the last. For every sum we line up the points, fill any empty column with a zero, then add. We check each answer together before the next sum appears.

Add the decimals: line up the points

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.

The bank rises from a clean tenths-only sum up to the cascade-regroup case. Watch for the 9.99 + 0.05 answer — pupils who forget the carry will write 9.104 instead of 10.04. When they slip, point back at the trailing-zero set-up rather than re-teaching from scratch.

+15 XP

6 - What Did We Notice? ~4 mins

MATHS TALK

Why is lining up the decimal points more important than lining up the right edge of the digits? What would go wrong if we lined up the edges instead?

Teacher Notes

Listen for pupils naming the decimal point as the thing that keeps tenths over tenths and hundredths over hundredths. Revoice a strong answer: 'so the point tells every digit which column it belongs to.' If a pupil says edges, gently show the 4.7 + 0.85 mis-set-up from Getting Started and let the class see the tenths landing in the hundredths place.

+10 XP

7 - What's Next ~2 mins

What we learned today

Line up the decimal points one under the other, not the right edge of the digits.
Fill any empty decimal place with a trailing zero so every column has a digit.
Add each column from the right, carrying a ten left just like with whole numbers.

Coming up

Next we look at subtracting decimals — the same line-up-the-points rule, with the same care for empty columns.

Teacher Notes

Keep this brisk. The trailing-zero habit is the one thing worth restating before pupils move to their activity-book practice.

+5 XP

Pupil practice

Module 2 · Operations and Computational Fluency Number

Lesson 19 · Adding Decimals: Line up the Points

Download Activity Book page (PDF)

End of lesson

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Teacher Class Feed

1 - Getting Started ~5 mins

2 - Watch and Notice ~11 mins

4.7 + 0.85 = 5.55

0.3 + 0.27 = 0.57

9.99 + 0.01 = 10.00

3 - Try It Together ~10 mins

Add the decimals together

4 - Set up Each Sum in Your Copy ~5 mins

5 - Class Challenge ~11 mins

Add the decimals: line up the points

6 - What Did We Notice? ~4 mins

7 - What's Next ~2 mins

What we learned today

Coming up

Unlock the full learning experience

XP