Length

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.