Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
In ancient times, people used body parts like handspan, cubit (length from elbow to fingertips), and foot-length for measurement. These were unreliable as they varied from person to person.
To bring uniformity, the French created the metric system in . Today, we use the International System of Units (SI units).
The SI unit of length is the metre (). Each metre is divided into equal parts called centimetres ().
Each centimetre has equal divisions called millimetres ().
For measuring large distances, the metre is not a convenient unit. We use the kilometre () instead.
Correct measurement requires placing the scale in contact with the object, starting from (or a known mark if the end is broken), and keeping the eye vertically above the point of measurement to avoid parallax error.
📐Formulae
💡Examples
Problem 1:
The distance between two cities is . Express this distance in kilometres.
Solution:
Explanation:
To convert metres to kilometres, we divide by because . Therefore, .
Problem 2:
While measuring the length of a knitting needle, the reading of the scale at one end is and at the other end is . What is the length of the needle?
Solution:
Explanation:
When the scale does not start from zero, the length is the difference between the two readings. Length .
Problem 3:
The height of a person is . Express it into and .
Solution:
and
Explanation:
To convert to : . To convert to : .