105
Writing lengths as decimals
Textbook: Part 3, lesson 105, pp. 107–109
GoalWriting lengths as decimals: the link between mm, cm, dm and m.
New words
length · uzunlikmillimetre · millimetrdecimetre · detsimetrmetre · metr
Explanation
Small units of length are tenths, hundredths and thousandths of larger ones. 1 mm = 0.1 cm = 0.01 dm = 0.001 m. 1 cm = 0.1 dm = 0.01 m. 1 dm = 0.1 m. To write a length given in several units as a decimal, express it in one unit: 3 dm 6 cm 2 mm = 3.62 dm = 36.2 cm; 4 m 2 dm 5 cm 9 mm = 4.259 m.
Worked examples
2 m 7 dm 3 cm = 2.73 m (7 dm = 0.7 m, 3 cm = 0.03 m).
6 dm 4 cm 7 mm = 64.7 cm (6 dm = 60 cm, 7 mm = 0.7 cm).
Class activity
“Measure and write”: children measure a notebook, pencil and eraser with a ruler and write the result in cm and mm, then as a decimal in centimetres (for example 17 cm 5 mm = 17.5 cm).
Practice
1
Express 6 m 3 dm 8 cm in metres as a decimal.
6.38
2
Express 4 dm 1 cm 6 mm in centimetres as a decimal.
41.6
3
Express 23 dm 4 cm in decimetres.
23.4
4
Express 9 dm 3 cm 6 mm in decimetres.
9.36
5
Write 4.06 m in metres and centimetres.
4 m 6 cm