Length: Measurement in Centimetre & Metres Basic 3 Mathematics Lesson Note

A. COUNTING SKILL: NUMBERS 841-860

Counting from 841 to 860: 841, 842, 843, 844, 845, 846, 847, 848, 849, 850, 851, 852, 853, 854, 855, 856, 857, 858, 859, 860

Practice counting:

• From 845 to 855: _______
• From 852 to 860: _______
• Backwards from 860 to 850: _______

Fill in missing numbers:

• 846, 847, _____, 849, _____
• 855, _____, 857, _____, 859
• _____, 842, _____, 844, _____

B. MEASURING IN CENTIMETRE (cm)

What is a centimetre? A centimetre (cm) is a small unit for measuring length.

Common lengths in centimetres:

• Length of your thumb = about 2cm
• Width of your finger = about 1cm
• Length of a pencil = about 15cm
• Length of a ruler = 30cm

Using a ruler:

• Always start measuring from 0
• Read the number where the object ends
• Write the answer with ‘cm’

Practice measuring: Draw lines and measure:

1. Draw a line 5cm long: _______
2. Draw a line 8cm long: _______
3. Draw a line 12cm long: _______

Measuring objects: Estimate, then measure:

1. Length of your exercise book = _____ cm
2. Width of your desk = _____ cm
3. Length of your shoe = _____ cm

C. MEASURING IN METRE (m)

What is a metre? 

A metre (m) is a bigger unit for measuring length. 1 metre = 100 centimetres (100cm)

Converting between metres and centimetres:

• 1m = 100cm
• 2m = 200cm
• 3m = 300cm
• 50cm = 0.5m (half metre)

Common lengths in metres:

• Height of a door = about 2m
• Width of a classroom = about 6m
• Height of your teacher = about 1.5m
• Length of a car = about 4m

Practice conversions:

1. 3m = _____ cm
2. 5m = _____ cm
3. 200cm = _____ m
4. 400cm = _____ m
5. 150cm = _____ m

Which unit to use:

• Use cm for small things (pencil, book, hand)
• Use m for big things (room, tree, person’s height)

Choose the right unit (cm or m):

1. Height of a tree: 8___
2. Length of a spoon: 15___
3. Width of a road: 10___
4. Length of an ant: 2___

D. REAL LIFE PROBLEMS INVOLVING LENGTH

Problem 1: Kemi’s pencil is 15cm long. Tolu’s pencil is 12cm long. How much longer is Kemi’s pencil? Answer: 15cm – 12cm = _____ cm

Problem 2: A rope is 3m long. Another rope is 2m long. If we join them together, how long will the new rope be? Answer: 3m + 2m = _____ m

Problem 3: Ada is 120cm tall. Her brother is 15cm taller than her. How tall is her brother? Answer: 120cm + 15cm = _____ cm

Problem 4: A classroom is 8m long. The blackboard is 3m long. How much space is left on the wall? Answer: 8m – 3m = _____ m

More practice problems:

1. A table is 150cm long. A cloth is 180cm long. How much cloth will hang over?
2. Two sticks measure 25cm and 35cm. What is their total length when placed end to end?
3. A garden is 12m long. A path through it is 8m long. How much garden is left?
4. Bola’s height is 115cm. She wants to reach something 140cm high. How much more does she need?

E. QUANTITATIVE REASONING

Comparing lengths: Which is longer?

1. 150cm or 1m? _____
2. 2m or 250cm? _____
3. 80cm or 1m? _____
4. 3m or 280cm? _____

Length patterns:

1. 10cm, 15cm, 20cm, _____, _____
2. 1m, 2m, 3m, _____, _____
3. 5cm, 10cm, 15cm, _____, _____

Estimation: Estimate these lengths:

1. Length of your classroom: about _____ m
2. Width of this book: about _____ cm
3. Height of your chair: about _____ cm
4. Length of a bus: about _____ m

Word problems with mixed units:

1. A stick is 2m long. Another stick is 50cm long. What is the total length in centimetres?
2. Kemi walks 3m, then 200cm more. How far did she walk altogether in metres?
3. A rope is 450cm long. How many metres and centimetres is this?

Logical thinking:

1. If 5 pencils placed end to end measure 75cm, how long is each pencil?
2. A room is 4m wide. How many 50cm tiles are needed to cover the width?

CLASS EXERCISES

1. Count from 848 to 858:
2. Fill missing numbers:
   1. 853, 854, _____, 856, _____
3. Convert lengths:
   1. 4m = _____ cm
   2. 300cm = _____ m
   3. 6m = _____ cm
   4. 150cm = _____ m
4. Choose the right unit (cm or m):
   1. Length of a classroom: 9___
   2. Width of a book: 20___
   3. Height of a building: 15___
   4. Length of a needle: 4___
5. Measure with your ruler:
   1. Draw and measure a line 7cm long
   2. Draw and measure a line 11cm long
6. Solve these problems:
   1. A rope is 2m long. Another is 150cm long. What is the total length in centimetres?
   2. Tolu is 125cm tall. His father is 30cm taller. How tall is his father?
   3. A stick is 80cm long. 25cm is cut off. How much is left?
7. Compare lengths:
   1. Which is longer: 2m or 180cm? _____
   2. Which is shorter: 90cm or 1m? _____
8. Complete patterns:
   1. 25cm, 30cm, 35cm, _____, _____
   2. 2m, 4m, 6m, _____, _____
9. Estimation:
   1. Estimate the length of your pencil: _____ cm
   2. Estimate the height of your teacher: _____ m
10. Problem solving: A garden path is 5m long. Street lamps are placed every 1m starting from the beginning. How many street lamps are needed?