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Adding and subtracting decimals – Year 6 maths lesson

Lesson 18 of 32 in the Year 6 maths course

UK version. UK school years, UK spelling and pounds (£). · US Math Department

A complete 45-minute lesson for Year 6 (ages 10–11) that runs on this page – at school or at home. Every answer is marked straight away, with a worked explanation.

Time
45 minutes + 20 min homework
Year
Year 6 (ages 10–11)
You need
Paper, a pencil and this page
Marked
Instantly, with explanations

For parents: how to use this lesson

You don't need to know this topic yourself. The lesson explains each step on screen, one tidy step at a time. Every answer is marked straight away with a worked explanation, so you never have to mark anything.

  1. Read what your child will learn and the big ideas together.
  2. Press Start the lesson below and sit with your child for the teaching and the worked examples (about 19 minutes).
  3. Let them do the practice on their own. They choose Getting started, On track or Challenge – start on On track and move up after a few right in a row.
  4. Finish with the exit ticket and the talk question: “Why do we fill empty places with zeros?”
  5. Later that day or the next day: the homework (20 minutes), then a practice test.

Watch out for

  • Lining up the last digits instead of the points (2.5 + 1.25 = 1.50). Line up the points first and fill gaps with zeros.
  • Forgetting the point in the answer. Bring the point straight down before you start.

Tip for home: Add up a few items on a receipt and check the total together.

What your child will learn

We are learning to add and subtract decimals by lining up the decimal points.

Success looks like

  • I can line up decimal points.
  • I can add and subtract decimals.
  • I can check with an estimate.

Key words

decimal point
separates the whole numbers from the parts
place holder
a zero that keeps digits in the right place
exchange
swap one of a place for ten of the next place
estimate
a quick, sensible answer

What to have ready

  • Paper and a pencil
  • This page on a computer, tablet or phone
  • For the hands-on part: Use real prices or lengths in metres: add two amounts and find the change or difference.

The big ideas (for the adult)

Write the numbers in columns with the decimal points lined up, so tenths are under tenths and hundredths under hundredths.

Fill empty places with zeros: 4.5 − 1.27 becomes 4.50 − 1.27.

Add or subtract from the right, exchanging just as with whole numbers, and keep the point in the answer lined up.

The lesson, step by step

45 minutes in 5 parts
PartTimeHow it is checked
Starter: quick recall5 minMarked by Classfern
Teaching input10 minNot assessed, self-checked
Worked examples and guided practice9 minNot assessed, marked by Classfern
Independent practice15 minMarked by Classfern
Plenary and exit ticket6 minMarked by Classfern, self-checked

Starter, "your turn", practice and exit ticket are marked by Classfern. Worked examples and teaching are not assessed. The hands-on task and the reflection are self-assessed. Explanations in talk are judged by the parent and not recorded.

The lesson

It runs here on the page. No sign-up and no names – progress is kept only in this browser.

Homework and practice at home

20 minutes: 10 practice questions, 3 multiple-choice questions and 2 to remember from earlier work, then a short reflection. New questions every time, all marked instantly.

More practice

All Year 6 maths lessons and tests · Maths Department

More Year 6 maths lessons

Curriculum

National Curriculum for England, Year 6: “solve problems involving number up to 3 decimal places”

Contains public sector information licensed under the Open Government Licence v3.0.

Our lessons and questions are our own. They are not written or endorsed by any government department, testing agency or exam board.