3
Review: length
Textbook: Part 1, lesson 3, pp. 10–12
GoalRecall how the units of length are related and convert between them.
New words
millimetre · millimetr (mm)centimetre · santimetr (sm)decimetre · detsimetr (dm)kilometre · kilometr (km)
Explanation
1 cm = 10 mm, 1 dm = 10 cm, 1 m = 10 dm = 100 cm, 1 km = 1 000 m. To write a compound measure in a smaller unit, convert each part and add. When adding, put equal units under each other.
Worked examples
4 m 6 dm 3 cm = 400 cm + 60 cm + 3 cm = 463 cm.
2 dm 7 cm 5 mm = 200 mm + 70 mm + 5 mm = 275 mm.
Class activity
“Measuring trip”: pairs measure a desk, a notebook and a door and write the result in m, dm, cm or mm. Then they compare answers with another pair.
Practice
1
How many centimetres is 5 m 2 dm 8 cm?
528
2
How many millimetres is 6 dm 4 cm 3 mm?
643
3
How many metres is 7 km?
7000
4
2 m 3 dm 4 cm + 1 m 5 dm 9 cm. Give the answer in centimetres.
393
5
1 m 25 cm was cut from a 3 m ribbon. How many centimetres of ribbon are left?
175