Good morning, children. Today, the topic that we learn
is “

**length**”.
The most common

**metric units of length**used are the**kilometre (km)**, the**metre (m)**, the**centimetre (cm)**and the**millimetre (mm)**.
These units of length are related as follows:

**1 cm = 10 mm**

**1 m = 100 cm**

**1 km = 1000 m**

We would measure the:

- thickness of the book in millimetres (mm).
- width of a computer screen in centimetres (cm).
- width of a road in metres (m).
- distance between two cities in kilometres (km).

We can use various instruments to measure length. For
example : We use rulers and tape measures that are marked in millimetres or
centimetres to measure shorter lengths accurately.

Now, we learn how to

**convert metric units**.
1)
To convert length

**from a larger unit into a smaller unit**,**multiply**by the relevant power of 10.
2)
To convert length

**from a smaller unit into a larger unit**,**divide**by the relevant power of 10.**Example:**

1)
Convert 15 cm to mm.

15 x 10mm
= 150 mm (
1cm = 10 mm )

2)
Convert 145.65 m to cm.

145.65
x 100 = 14565 cm ( 1m = 100
cm )

3)
Convert ¾ km to m.

¾ x
1000 = (3000 ÷ 4) cm ( 1 km =
1000 m )

= 750 cm

4)
Convert 60 mm to cm.

60 ÷
10 cm = 6 cm (
1cm = 10 mm )

5)
Convert 8075 cm to m.

8075
÷ 100 m = 80.75 m ( 1m = 100 cm )

6)
Convert 750 000 m to km.

750
000 ÷ 1000 km = 750 km ( 1 km =
1000 m )

You
should be able to work confidently with metric units to solve problems in daily
life.

Have
a happy day and see you tomorrow.

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