means how long something is. We see many things around us. Some are short in
length such as paper clip, pencil, pen, notebook etc., some are long in length
such as tree, electric pole, cloth, room, train track and some are very long
such as distance between two places. We need to select suitable unit to measure
Non Standard Units of Measurement
early days body parts were used to measure length. But measurements taken by
these means are not accurate and consistent. If we use our hand span to measure
length, the measurement taken by different person will vary as our hand spans
are not equal.
Example: a child hand span is smaller than the
adult. So, hand span, hand, foot and cubit are not standard units of measurement.
Standard Units of Measurement
observed that nonstandard unit of measurement does not give same results. So,
we need to use some standard units for measuring lengths. Otherwise the
measurements of an object will be different when measured in different ways. We
use different units of length to measure different lengths.
Example: We measure length of table edge, length of
chalk, length of pencil etc. in centimeters (cm), length of a room, height of
tree, length of cloth, height of an electric pole etc. in meters (m) and longer
distance such distance between two places in kilometers (km).
Points to be remembered
standard unit of length is meter.
meter is divided into 100 smaller units called centimeters.
1m = 100cm
form of meter is “m”, centimeter is “cm” and kilometer is “km”.
m put together to make a bigger unit called a kilometer.
Instrument of Measurement of Length
use metric ruler, metric stick, tape, rod etc. to measure length.
Example 1: Length
of blue rope is 7m and length of red rope is 5m. Which rope is bigger and by
Example 2: Ria travelled 2km by car and 5 km by bus.
How much distance did she travel in all?