You will learn
- Line up decimal points.
- Add with regrouping.
- Add whole and decimal.
- Estimate first.
Version 0.2 · expanded edition · built from cited public sources Content is based on the official frameworks and sources listed under Sources and standards. No official endorsement is claimed. Written in the style of common primary school assessments. No exam result is promised.
Student lesson
- Line up the decimal points.
- Fill empty places with zeros.
- Add from the right and regroup.
- Estimate first to check.
Words to know
Result of adding.
Line up.
Carry.
Close guess.
1. Discover: shopping total
Bread costs 3.45 and milk 2.70. What is the total?
2. Understand: adding decimals
- Line up the points: 3.45 + 2.70 = 6.15.
- 12.5 + 0.75 = 12.50 + 0.75 = 13.25.
- 0.6 + 0.35 = 0.95.
- 7 + 0.45 = 7.45.
Idea 1: Line up
4.08 + 1.9: write 4.08 + 1.90 = 5.98.
Idea 2: Zeros
0.6 + 0.35 = 0.60 + 0.35 = 0.95. 7 + 0.45 = 7.00 + 0.45 = 7.45.
Idea 3: Regroup
12.5 + 0.75 = 12.50 + 0.75 = 13.25. 2.5 + 3.75 = 6.25.
Why line up points? Only matching places can be added.
3. Worked examples
Example 1 (I show you): Add
4.08 + 1.9
- 4.08 + 1.90.
- Add columns.
Answer: 5.98
Example 2 (We do it together): Add
12.5 + 0.75
- 12.50 + 0.75.
Answer: 13.25
Example 3 (You try): Add
7 + 0.45
Show the steps and answer
- 7.00 + 0.45.
Answer: 7.45
Did you know?
The decimal point in the answer sits directly under the other points.
Why this matters
Adding decimals is used in shopping, measuring and sport.
4. Explore: add
You need paper.
- Line up points.
- Fill with zeros.
- Add right to left.
- Place the point.
Think about it: what did you notice?
6.15.
5. Practise
Say it in a sentence
Use these starters when you talk about the lesson. Say them out loud.
- I line up the ___.
- I write ___ as ___.
- I add the ___ first.
- The sum is ___.
Guided practice
Question 1. 3.45 + 2.70?
6.15.
Question 2. 12.5 + 0.75?
13.25.
Question 3. 0.6 + 0.35?
0.95.
Independent practice
Level 1: Start
- 4.08 + 1.9
- 0.6 + 0.35
- 12.5 + 0.75
- 7 + 0.45
- 2.5 + 3.75
Level 2: Grow
- 1.2 + 3.4
- 0.5 + 0.25
- 6 + 0.3
Level 3: Stretch
- 8.75 + 14.6
- 0.456 + 0.5
- Ben says 2.5 + 3.75 = 6.80. What is wrong?
Answers are in the answer key below. Try first, then check.
6. Apply: everyday mathematics
Bread 3.45 and milk 2.70. Total?
Show a sample answer
6.15.
Another one. Ama buys 2.5 kg of yam and 1.75 kg of rice. How much in total?
Show a sample answer
4.25 kg
7. Common mistakes
Fix: Line up the points.
Fix: Line up the decimal points.
Fix: Place it under the other points.
8. Lesson summary and revision card
- I can line up decimals.
- I can add with regrouping.
- I can add whole numbers and decimals.
- I can estimate first.
9. Check and master
Answer all 14 questions. You will see feedback after each one.
Your result appears here after you answer every question.
10. Key takeaways
- Align the points.
- Fill with zeros.
- Estimate to check.
11. Next lesson
Next lesson: Decimal subtraction. Keep going with the next idea in this course.
Exam practice
These questions are written in the style of common school and international primary assessments. Try them on your own, without looking back. Then check your answers in the marking guide. The marks are shown in brackets.
- Work out 4.08 + 1.9. [3 marks]
- Work out 0.6 + 0.35. [2 marks]
- Work out 12.5 + 0.75. [3 marks]
- Work out 7 + 0.45. [2 marks]
- Ali says 2.5 + 3.75 = 6.80. Is he right? Explain. [3 marks]
Total: 13 marks.
Marking guide and model answers
- Line up the decimal points: 4.08 + 1.90 [1]; add columns with regrouping [1]; 5.98 [1]
- 0.60 + 0.35 [1]; 0.95 [1]
- 12.50 + 0.75 [1]; add the columns [1]; 13.25 [1]
- 7.00 + 0.45 [1]; 7.45 [1]
- No [1]. Line up the decimal points: 2.50 + 3.75 [1]. The answer is 6.25 [1].
Score guide: 12 to 13 = secure. 8 to 11 = nearly there, revise the parts you missed. Under 8 = work through the lesson again with a grown-up.
Printable worksheet
- 4.08 + 1.9
- 0.6 + 0.35
- 12.5 + 0.75
- 7 + 0.45
- 2.5 + 3.75
- 4.08 + 1.9
- 0.6 + 0.35
- 12.5 + 0.75
- 7 + 0.45
- 2.5 + 3.75
Homework
Add the prices of three things you buy.
Answer key and marking scheme
| Question | Expected response | Marks |
|---|---|---|
| 4.08 + 1.9 | 5.98 | 2 |
| 0.6 + 0.35 | 0.95 | 2 |
| 12.5 + 0.75 | 13.25 | 2 |
| 7 + 0.45 | 7.45 | 2 |
| 2.5 + 3.75 | 6.25 | 2 |
| Total | 10 |
Practice answers: Worksheet: 1 5.98; 2 0.95; 3 13.25; 4 7.45; 5 6.25.
Quiz answers: 1 A, 2 B, 3 C, 4 A, 5 B, 6 A, 7 B, 8 C, 9 A, 10 B, 11 C, 12 A, Challenge 1 C, Challenge 2 C.
Extra worksheet answers (items 6 onward): 6 5.98; 7 0.95; 8 13.25; 9 7.45; 10 6.25.
Independent practice answers. Level 1: 1 5.98; 2 0.95; 3 13.25; 4 7.45; 5 6.25. Level 2: 1 4.6; 2 0.75; 3 6.3. Level 3: 1 23.35; 2 0.956; 3 Line up the points: 2.50 + 3.75 = 6.25..
Mastery and remediation
| Objective | Bronze (Developing) | Silver (Proficient) | Gold (Advanced) |
|---|---|---|---|
| O1 Line up decimal points | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O2 Add with regrouping | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O3 Add whole and decimal | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O4 Estimate first | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
Courseversity badge thresholds (overall quiz score): Gold = 90–100%; Silver = 80–89.9%; Bronze = 70–79.9%. A badge is never a full record of progress.
If a learner struggles
- Find the misconception: Lining up the right-hand digits. Line up the points.
- Explain another way: use real objects first, then pictures.
- Show a simpler example: Money addition.
- Guided practice: work through one example together and let the learner try the next one.
- Reassess: use the quiz again or the worksheet.
- Move on when the learner shows Silver-level evidence independently.
For parents and guardians
In this lesson your child adds decimals. You do not need to be good at mathematics to help.
- Add prices in a shop.
- Ask: are the points lined up?
- Estimate before adding.
- Ask “how do you know?” after each answer, and listen.
- Praise effort, not only right answers. Mistakes are how we learn.
- Ten to fifteen minutes a day is better than one long session.
Teacher package
1–5. Objectives, prerequisites, materials, preparation, duration
Lesson objectives. Learners will: line up decimal points; add with regrouping; add whole and decimal; estimate first.
Prerequisite knowledge. Lesson 2.
Materials. Counters (stones, seeds or bottle tops), paper, pencils, board or chalkboard. Low-resource options: use stones, seeds, sticks, bottle tops or drawings in the sand or on the board instead of printed materials.
Preparation. Gather the counters and draw the example pictures on the board before the lesson.
Suggested duration. 45–60 minutes. It can be split into two shorter sessions.
6–9. Teaching procedure, explanation notes, guided and independent activities
Introduction (5 min). Start with the Discover situation and let learners suggest ideas before you teach.
Explanation (10 min). Teach the Understand section with real objects first, then pictures, then symbols and words.
Guided activity (10 min). You need paper. Learners follow the Explore steps in pairs.
Independent activity (10 min). Learners complete the independent practice and the worksheet.
Assessment and reflection (5 min). Ask each learner to say one thing they learned and how they know it.
Key questions. Are the points lined up? Do I need to regroup?
Teacher explanation notes. Use the concrete, pictorial, abstract order: real objects first, then pictures, then symbols and words. Return to real objects whenever a learner needs support.
10–12. Differentiation, formative assessment, common misconceptions
Support. Use real objects and work with a partner; say each step aloud together. Extension. Ask learners to make up their own example and explain it to a partner.
Formative assessment. Listen to learner explanations, ask “how do you know?”, and check the independent work.
Misconceptions. Lining up the right-hand digits. Line up the points.
13–15. Assessment questions, answer keys, marking scheme
Use the quiz and worksheet on this page. The 13-mark exam practice scheme, the 10-mark scheme and all answers are in the answer sections above. Re-check every answer and the marking scheme before publication.
16–19. Remediation, enrichment, homework, teacher reflection
Remediation. Money addition. Enrichment. Invite learners to find or create three more examples at home or in the classroom and explain them. Homework. See above.
Teacher reflection. After teaching, record: which concepts learners understood; which misconceptions occurred; which activities worked; which learners need more practice; and what to improve next time.
Sources and standards
This lesson is based on the sources below, and no official endorsement is claimed. Reference starting points named in the Courseversity standard: Common Core State Standards for Mathematics, Cambridge Primary and the IB Primary Years Programme. Where a standard code is named, it points to the official framework.
Official standards for this topic area. Common Core State Standards for Mathematics (official site): Grade 6 » Ratios & Proportional Relationships; Grade 6 » The Number System. These pages list the standards that cover this topic area; read them alongside the lesson.
Research used to shape this lesson. Common Core 5.NBT.B.7; Cambridge Primary Mathematics Stage 6 (adding decimals). These sources informed the lesson.