You will learn
- Change to the same unit before comparing.
- Compare lengths, masses and capacities.
- Find the difference.
- Order measurements.
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
- Change to the same unit first.
- Compare lengths, masses and capacities.
- Subtract to find the difference.
- Order from smallest to biggest.
Words to know
Say which is more.
How much more or less.
The same measure for both.
Arrange in a line.
1. Discover: rope or ribbon?
One rope is 2 m long and another is 150 cm. Which is longer? How much longer?
2. Understand: comparing measurements
To compare, change both to the same unit. 2 m = 200 cm, so 2 m is longer than 150 cm by 200 − 150 = 50 cm.
2 kg vs 1,800 g: 2 kg = 2,000 g, so 2 kg is heavier by 200 g. 1 L vs 900 ml: 1 L = 1,000 ml, so 1 L holds 100 ml more.
1 m 20 cm − 85 cm: 120 − 85 = 35 cm.
Idea 1: Same unit
2 m or 150 cm? 2 m = 200 cm, so 2 m is longer. 1 L or 900 ml? 1 L = 1,000 ml, so 1 L is more.
Idea 2: Difference
1 m 20 cm − 85 cm = 120 cm − 85 cm = 35 cm.
Idea 3: Order
1 kg, 800 g, 1,200 g in grams: 1,000; 800; 1,200. From lightest: 800 g, 1 kg, 1,200 g.
Why change units? We can only compare numbers in the same unit.
3. Worked examples
Example 1 (I show you): Longer
2 m or 150 cm?
- 2 m = 200 cm.
Answer: 2 m
Example 2 (We do it together): Difference
1 m 20 cm − 85 cm
- 120 − 85.
Answer: 35 cm
Example 3 (You try): Order
1 kg, 800 g, 1,200 g from lightest.
Show the steps and answer
- 1,000 g; 800 g; 1,200 g.
Answer: 800 g, 1 kg, 1,200 g
Did you know?
1 kg is more than 900 g even though 1 is less than 900.
Why this matters
Comparing measures helps us choose, buy and build.
4. Explore: rope battle
You need string and a ruler.
- Measure two ropes in different units.
- Change to the same unit.
- Compare.
- Find the difference.
Think about it: what did you notice?
The longer rope is the bigger number in the same unit.
5. Practise
Say it in a sentence
Use these starters when you talk about the lesson. Say them out loud.
- I change ___ to ___.
- ___ is longer / heavier / more because ___.
- The difference is ___.
- In order: ___.
Guided practice
Question 1. 2 m or 150 cm: longer?
2 m.
Question 2. 2 kg or 1,800 g: heavier?
2 kg.
Question 3. 1 m 20 cm − 85 cm?
35 cm.
Independent practice
Level 1: Start
- 2 m or 150 cm
- 2 kg or 1,800 g
- 1 L or 900 ml
- Difference between 1 m 20 cm and 85 cm
- Order 1 kg, 800 g, 1,200 g
Level 2: Grow
- 3 m or 250 cm?
- 500 g or 1 kg?
- 750 ml or 1 L?
Level 3: Stretch
- 2 m 10 cm − 95 cm
- Order from least: 2 L, 1,500 ml, 2,100 ml
- Ben says 900 ml is more than 1 L because 900 is bigger than 1. What is wrong?
Answers are in the answer key below. Try first, then check.
6. Apply: everyday mathematics
A rope is 2 m and a ribbon 150 cm. How much longer is the rope?
Show a sample answer
50 cm.
Another one. Bola has 1 m 20 cm of cloth and Ade has 95 cm. Who has more and by how much?
Show a sample answer
Bola, by 25 cm
7. Common mistakes
Fix: Change to the same unit first.
Fix: Change to the same unit.
Fix: Make both the same unit first.
8. Lesson summary and revision card
- I can change to the same unit.
- I can compare lengths, masses and capacities.
- I can find the difference.
- I can order measurements.
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
- Same unit first.
- Subtract for the difference.
- Order in the same unit.
11. Next lesson
Next lesson: Estimation. 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.
- Which is longer, 2 m or 150 cm? [2 marks]
- Which is heavier, 2 kg or 1,800 g? [2 marks]
- Find 1 m 20 cm − 85 cm. [2 marks]
- Order from lightest: 1 kg, 800 g, 1,200 g. [2 marks]
- Ali says 900 ml is more than 1 L. Is he right? Explain. [3 marks]
Total: 11 marks.
Marking guide and model answers
- 2 m = 200 cm [1]; 2 m [1]
- 2 kg = 2,000 g [1]; 2 kg [1]
- 120 − 85 [1] = 35 cm [1]
- 1,000; 800; 1,200 [1]; 800 g, 1 kg, 1,200 g [1]
- No [1]. 1 L = 1,000 ml [1]. 1,000 ml is more than 900 ml [1].
Score guide: 10 to 11 = secure. 7 to 9 = nearly there, revise the parts you missed. Under 7 = work through the lesson again with a grown-up.
Printable worksheet
- Longer: 2 m or 150 cm
- Heavier: 2 kg or 1,800 g
- More: 1 L or 900 ml
- 1 m 20 cm − 85 cm
- Lightest of 1 kg, 800 g, 1,200 g
- Longer: 2 m or 150 cm?
- Heavier: 2 kg or 1,800 g?
- More: 1 L or 900 ml?
- 1 m 20 cm − 85 cm =
- 2 kg − 1,800 g =
Homework
Compare the mass of three foods at home using the same unit.
Answer key and marking scheme
| Question | Expected response | Marks |
|---|---|---|
| Longer: 2 m or 150 cm | 2 m | 2 |
| Heavier: 2 kg or 1,800 g | 2 kg | 2 |
| More: 1 L or 900 ml | 1 L | 2 |
| 1 m 20 cm − 85 cm | 35 cm | 2 |
| Lightest of 1 kg, 800 g, 1,200 g | 800 g | 2 |
| Total | 10 |
Practice answers: Worksheet: 1 2 m; 2 2 kg; 3 1 L; 4 35 cm; 5 800 g.
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 2 m; 7 2 kg; 8 1 L; 9 35 cm; 10 200 g.
Independent practice answers. Level 1: 1 2 m; 2 2 kg; 3 1 L; 4 35 cm; 5 800 g, 1 kg, 1,200 g. Level 2: 1 3 m; 2 1 kg; 3 1 L. Level 3: 1 115 cm; 2 1,500 ml, 2 L, 2,100 ml; 3 The units differ. 1 L = 1,000 ml, which is more..
Mastery and remediation
| Objective | Bronze (Developing) | Silver (Proficient) | Gold (Advanced) |
|---|---|---|---|
| O1 Change to the same unit before comparing | 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 Compare lengths, masses and capacities | 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 Find the difference | 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 Order measurements | 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: Comparing numbers in different units. Change to the same unit first.
- Explain another way: use real objects first, then pictures.
- Show a simpler example: Convert to the small unit and compare.
- 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 compares and orders measurements. You do not need to be good at mathematics to help.
- Compare two bottles or two ropes.
- Ask: are the units the same?
- Order a few items by mass.
- 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: change to the same unit before comparing; compare lengths, masses and capacities; find the difference; order measurements.
Prerequisite knowledge. Lesson 4.
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 string and a ruler. 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 units the same? Which is more? What is the difference?
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. Comparing numbers in different units. Change to the same unit first.
13–15. Assessment questions, answer keys, marking scheme
Use the quiz and worksheet on this page. The 11-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. Convert to the small unit and compare. 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 3 » Measurement & Data. These pages list the standards that cover this topic area; read them alongside the lesson.
Research used to shape this lesson. Common Core 3.MD.A.2 and 4.MD.A.2; Cambridge Primary Mathematics Stage 3 (comparing measures). These sources informed the lesson.