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Standard Units of Length

To make our judgement more reliable and accurate, we should have a common set

of standard units of measurement. Scientists all over the world accepted a set of
standard units for the sake of uniformity.

The fixed measurements for measuring lengths are centimetres and metres.
Centimetre

This is a centimetre. We write centimetre as cm.

cm cm

Note
We use the word ‘about’ to
show that the measurement
About 1 cm About 3 cm About 15 cm is not exact.

We use a 15 cm or 30 cm ruler to measure shorter lengths.

Measuring Length Using a Ruler (Scale)

To measure the length of an object with a ruler, we follow these steps:

Step 1. Place the ruler adjacent to the object along its length.

Step 2. Adjust the object so that its one end could be alongwith the zero mark of
the ruler.

Step 3. Look at the other end
of the object and read

carefully the mark aligned
with this end of the object. It gives us the length of the object. Here, it is

10 cm. Thus, the length of the above pencil is 10 cm.

Quick Check
What is the length of the spoon?

______ cm

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