Practice Units of length
Length measures distances in units such as millimetres, centimetres and metres.
Use a common unit before comparing or adding measurements.
Exercises with solutions
Lengths are given in different units. The conversion factor is 10, 100 or 1000: 1 km = 1000 m, 1 m = 10 dm = 100 cm = 1000 mm. To convert to a smaller unit you multiply, to a larger unit you divide.
Exercise 1
How many centimetres are 2.4 m?
Show solution and working
240 cm
1 m = 100 cm, so 2.4 · 100 cm = 240 cm.
Exercise 2
How many metres are 3,500 mm?
Show solution and working
3.5 m
1 m = 1000 mm, so 3,500 ÷ 1000 = 3.5 m.
Exercise 3
Convert 1 km 250 m into metres.
Show solution and working
1,250 m
1 km = 1000 m. Adding the 250 m gives 1,250 m.
Exercise 4
A rope is 4.5 m long. How many 50 cm pieces do you get?
Show solution and working
9 pieces
First use the same unit: 4.5 m = 450 cm. Then 450 cm ÷ 50 cm = 9.
Common mistake
Converting in the wrong direction: from metres to centimetres the number grows, from centimetres to metres it shrinks. Write the unit at every step so a mistake shows up immediately.
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