7.11.2 Converting Lengths & Areas

How do I convert between units for lengths?

• For metric units, conversion can be done by simply multiplying or dividing by powers of 10
• You need to know the basic conversions:
  • 1 cm = 10 mm
  • 1 m = 100 cm
  • 1 km = 1000 m
• You can do the conversion in stages
  • E.g.
    First convert kilometres into metres then meters into centimetres
• If you are given an imperial conversion (such as miles to kilometres) then you can use ratios to help with the conversions
  • E.g.
    There are 5 miles in 8 kilometres so to find how many miles are in 13 kilometres you would solve 

How do I convert between units for areas?

• Converting units for areas is slightly trickier
• You need to remember to square the conversion rates
  • This is because area is 2D
  • The fact the units have a "squared" on them will help you remember
• You need to be able to use the basic conversions
  • 1 cm² = 10² mm² = 100 mm²
  • 1 m² = 100² cm² = 10 000 cm²
  • 1 km² = 1000² m² = 1 000 000 m²
• There are also less common conversions
  • 1 hectare (ha) = 10 000 m²
• If you are given an imperial conversion (such as miles to kilometres) for lengths:
  • Write the conversion as a ratio
    • E.g. Miles to kilometres is 5 : 8
  • Square the numbers to get the ratio for the conversion of the units for area
    • E.g. Miles² to kilometres² is 25 : 64