You will learn
- Choose a unit for length.
- Read a ruler to the nearest centimetre and millimetre.
- Say that 1 cm = 10 mm, 1 m = 100 cm and 1 km = 1,000 m.
- Measure a line.
Version 0.1 · published for early use · expert review pending Standards alignment: pending verification. Not yet reviewed against the Courseversity scorecard.
Student lesson
Words to know
A very small unit of length.
10 millimetres.
100 centimetres.
1,000 metres.
1. Discover: how long is it?
How would you measure a pencil, a classroom and the distance between two towns? Would you use the same unit?
2. Understand: measuring length
We measure length with standard units.
- mm for tiny things; 1 cm = 10 mm.
- cm for a pencil or book; 1 m = 100 cm.
- m for a room or a rope; 1 km = 1,000 m.
- km for long distances between towns.
Put the 0 mark of the ruler at one end. A line from 2 to 9 on the ruler is 9 − 2 = 7 cm. A pencil of 14 cm is 140 mm. 2 m 30 cm = 230 cm.
3. Explore: measure it
You need a ruler and some objects.
- Measure a pencil in cm and mm.
- Measure the width of a desk in cm.
- Measure the classroom with a tape in m.
- Record all in a table.
Think about it: what did you notice?
Answers vary; 14 cm = 140 mm.
4. Practise
Guided practice
Question 1. 1 cm in mm?
10 mm.
Question 2. Unit for the distance between towns?
km.
Question 3. 2 m 30 cm in cm?
230 cm.
Independent practice
- 14 cm in mm
- 1 m in cm
- 1 km in m
- A line from 3 to 11 on a ruler
- 3 m in cm
Answers are in the answer key below. Try first, then check.
5. Apply: everyday mathematics
A rope is 2 m 30 cm long. How many centimetres is that?
Show a sample answer
230 cm.
6. Common mistake
Fix: Always start at 0.
7. Check and master
Answer all questions. You will see feedback after each one.
Your result appears here after you answer every question.
8. Key takeaways
- Choose the right unit.
- Start at 0.
- Know the conversions.
9. Next lesson
Next lesson: Measuring mass. Keep going with the next idea in this course.
Printable worksheet
- 14 cm in mm
- 1 m in cm
- 1 km in m
- Line from 3 to 11
- 3 m in cm
Homework
Measure five things at home in cm and mm.
Answer key and marking scheme
| Question | Expected response | Marks |
|---|---|---|
| 14 cm in mm | 140 | 2 |
| 1 m in cm | 100 | 2 |
| 1 km in m | 1,000 | 2 |
| Line from 3 to 11 | 8 cm | 2 |
| 3 m in cm | 300 | 2 |
| Total | 10 |
Practice answers: Worksheet: 1 140; 2 100; 3 1,000; 4 8 cm; 5 300.
Quiz answers: 1 A, 2 B, 3 C, 4 A, 5 B, challenge C.
Mastery and remediation
| Objective | Bronze (Developing) | Silver (Proficient) | Gold (Advanced) |
|---|---|---|---|
| O1 Choose a unit for length | 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 Read a ruler to the nearest centimetre and millimetre | 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 Say that 1 cm = 10 mm, 1 m = 100 cm and 1 km = 1,000 m | 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 Measure a line | 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 |
Proposed Courseversity thresholds for this page: Bronze = at least 3 of 5 core questions correct; Silver = all 5; Gold = all 5 plus the challenge. A badge is never a full record of progress.
If a learner struggles
- Find the misconception: Starting at 1 instead of 0. Always start at 0.
- Explain another way: use real objects first, then pictures.
- Show a simpler example: Use cubes first, then a ruler.
- 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.
Teacher package
1–5. Objectives, prerequisites, materials, preparation, duration
Lesson objectives. Learners will: choose a unit for length; read a ruler to the nearest centimetre and millimetre; say that 1 cm = 10 mm, 1 m = 100 cm and 1 km = 1,000 m; measure a line.
Prerequisite knowledge. Grade 2 cm and m.
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. 35–45 minutes.
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 a ruler and some objects. 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.
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. Starting at 1 instead of 0. Always start at 0.
13–15. Assessment questions, answer keys, marking scheme
Use the quiz and worksheet on this page. The 10-mark scheme and all answers are in the answer key above. Re-check every answer and the marking scheme before publication.
16–19. Remediation, enrichment, homework, teacher reflection
Remediation. Use cubes first, then a ruler. 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
Alignment is pending verification and no external 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. Specific standard codes will be added once checked against the official documents.