Question

(a) Why do we use standard unit of length for measurements?
(b) Arrange the following lengths in their increasing magnitude:
1 metre, 1 centimetre, 1 kilometre, 1 millimetre.

Answer 1

(a) In ancient times, people used length of a foot, the width of a finger, the distance of a step as units of measurement. This caused confusion and a need to develop a uniform system of measurement arose. Hence, a common unit of length is decided and all the measurements is done according to that unit of length.

(b) Since, 1 kilometre = 1000 metre
So, 1 kilometre > 1 metre

And 1 metre = 100 centimetre
So, 1 metre > 1 centimetre

And 1 centimetre = 10 millimetre
i.e 1 centimetre > 1 millimetre
Thus,
Ascending order of length:
1 millimetre < 1 centimetre < 1 metre < 1 kilometre