This chapter teaches students about measurement of length using standard units — millimetre (mm), centimetre (cm), metre (m), and kilometre (km). Students learn when to use each unit depending on the size of the object or distance.
The chapter focuses on converting lengths between different units and comparing them by first writing them in the same unit. Tools like the double number line help in understanding conversions clearly.
Students solve real-life problems involving:
Addition and subtraction of lengths
Comparing heights and distances
Measuring and drawing line segments
Converting between cm, mm, m, and km
Through examples like statue heights, train journeys, races, and daily measurements, students understand how length is used in everyday life.
Overall, this chapter builds practical skills in measuring, converting, and comparing distances accurately.
Key Points
• Standard Units of Length:
1 cm = 10 mm
100 cm = 1 m
1 km = 1,000 m
• Choosing Units Wisely:
Use mm for very small lengths (like coin thickness), cm for small-medium (like pencil), m for room or door heights, km for long distances (between cities)
• Conversion & Comparison:
Convert measurements to the same unit (e.g., cm to m) before comparing using <, >, = signs
• Double Number Lines help convert and compare measurements visually (e.g., a sari's length in different units)
• Practical Examples:
Example: 456 cm vs 5 m → convert → 456 cm < 500 cm
Some lengths are exactly equal (e.g., 2 m 150 cm = 3 m 50 cm = 350 cm)
• Real-Life Applications:
Statue Heights: Calculate differences (e.g., Statue of Unity 182 m and Statue of Liberty 93 m → difference 89 m) and identify pairs with least or greatest difference
Kilometre Race: 3 km race with water stations every 500 m → stations at 500 m, 1,000 m, etc.
Longest Train Journey in India: Dibrugarh to Kanyakumari = 4,187 km; compare distances between stations (e.g., Guwahati–Dimapur vs Bhubaneswar–Jalpaiguri)
• Measuring & Drawing:
Draw lines in cm and mm; convert 36 mm = 3 cm 6 mm; use a ruler to measure and convert
• Conversions across Units:
Convert between cm, mm, m, km (e.g., 34 km = 34,000 m; 5,792 cm = 57 m 92 cm)
• Everyday Word Problems:
Total ribbon length: 3 m 75 cm + 2 m 25 cm = 6 m
Difference between distances (e.g., between waterfall and Sanchi): 48 km 700 m – 17 km 900 m = 30 km 800 m
Combine segments: 2 km 300 m + 2 km 650 m = 4 km 950 m
Shared measurement conversions for daily use
👉 👉Understanding Far and Near teaches us more than numbers—it teaches us about measurement in real life. Knowing the right unit, converting accurately, and comparing properly helps us make sense of the world around us, from planning journeys to measuring objects at home.