Measurements

Measuring Length

To know how long an object is, or how tall, or how far apart two objects are, we need to measure the length. We can tell lengths of something just by observation but to know the exact length we need to measure it.

• To measure the length of something we use non-standard units of length. Such as handspan, footspan, finger width, etc.
• The drawback of non-standard units is that these things change person to person or object to object.
  

• To measure the lengths more precisely, we use standard units.
• Standard units are pre-defined and do not change person to person or object to object.
• To measure length in standard unit, we use different tools such as ruler, measuring tapes, ropes, metre sticks, etc.
• Lengths can be measured in different units. Some of the units are:
  • Kilometre (km)
  • Metre (m)
  • Centimetre (cm)
  • Millimetre (mm)

Relation Between Different Units

• One Kilometre is equal to 1000 Metres.
• One Metre is equal to 100 Centimetres.
• One Centimetre is equal to 10 Millimeters.

Conversion of Units

• To convert Kilometre to Metre, we multiply it by 1000. To convert Metre to Kilometre, we divide it by 1000.
• To convert Metre to Centimetre, we multiply it by 100. To convert Centimetre to Metre, we divide it by 100.
• To convert Centimetre to Millimetre, we multiply it by 10. To convert Millimetre to Centimetre, we divide it by 10.

Selection of appropriate measurement units:

• Length of very small things should be measured in millimeters (mm).
• Lengths larger than 10 mm but smaller than a metre should be measured in centimeters.
• Lengths larger than a metre should be measured in meters.
• Very large distances should be measured in kilometers.