Length — cm, m and km

• Understand and convert between millimetres, centimetres, metres and kilometres.
• Use 1 m = 100 cm and 1 km = 1,000 m to solve problems.
• Solve real-life length word problems (distance walked, cloth measured, etc.).

Level 1 — Units of length

Verbal: We measure short lengths in centimetres (cm), medium lengths in metres (m), and long distances in kilometres (km).

Level 2 — Converting metres to centimetres

Symbolic: 5 m = 5 × 100 = 500 cm. 5 m 20 cm = 500 + 20 = 520 cm.

Level 3 — Converting kilometres to metres

Symbolic: 3 km = 3 × 1,000 = 3,000 m. 3 km 250 m = 3,000 + 250 = 3,250 m.

Level 4 — Real-life word problems

Example: Meena's house is 1 km 200 m from school, and the market is 350 m further from school in the same direction. Total to market from Meena's house passing school = 1,200 m + 350 m = 1,550 m.

NCERT anchor: Math-Magic 4, Ch 2 — Long and Short (measuring length, units cm/m/km).

Rohan walked 2 km 400 m in the morning and 650 m in the evening. How far did he walk in all (in metres)?

Step 1 — Convert 2 km 400 m to metres: 2 × 1,000 + 400 = 2,400 m.
Step 2 — Add the evening walk: 2,400 m + 650 m = 3,050 m.
Answer: 3,050 m (or 3 km 50 m).

• 7 m = ___ cm (700 cm)
• 4 km 100 m = ___ m (4,100 m)
• 250 cm = ___ m ___ cm (2 m 50 cm)
• 6,500 m = ___ km ___ m (6 km 500 m)
• Stretch: A rope is 3 m 40 cm long. Another rope is 215 cm long. Which rope is longer, and by how much? (First rope; 340 cm vs 215 cm → longer by 125 cm)

Revision tip: Measure your school bag's strap or your arm with a ruler in cm, then convert to m — it makes the unit relationship stick.

Open the Practice tab for graded questions on Length.