Converting between Units (Edexcel IGCSE Maths)

Converting Units

Spec point — 4.10F

How do I convert units of lengths?

• For metric units, conversion can be done by simply multiplying or dividing by powers of 10

• You need to know the basic conversions for length

  • 1 cm = 10 mm
  • 1 m = 100 cm
  • 1 km = 1000 m

• You need to decide whether to multiply or divide by the conversion factor

  • Ask, does the number of units increase or decrease?

    • The number of mm is 10 times bigger than the number of cm so mm = cm × 10

• You can do the conversion in stages

  • First convert kilometres into metres then metres into centimetres

How do I convert units of mass?

• For metric units, conversion can be done by simply multiplying or dividing by powers of 10

• You need to know the basic conversions for mass

  • 1 g = 1000 mg
  • 1 kg = 1000 g
  • 1 tonne = 1000 kg

How do I convert units of volume/capacity?

• For metric units, conversion can be done by simply multiplying or dividing by powers of 10

• You need to know the basic conversions for capacity

  • 1 litre = 100 cl = 1000 ml

    • 1 cl = 10 ml

• You must know the basic conversion between volume and capacity

  • 1 ml = 1 cm³
  • 1 litre = 1000 ml = 1000 cm³
  • 1 m³ = 1000 litres

Worked Example Convert

(a) 54 cm to mm

Answer:

1 cm = 10 mm

54 cm = (54 × 10) mm

Final answer: 540 mm

(b) 12 300 cm to km

Answer:

First convert from cm to m 100 cm = 1 m

12 300 cm = (12 300 ÷ 100) m = 123 m

Now convert from m to km 1000 m = 1 km

123 m = (123 ÷ 1000) km

Final answer: 0.123 km

(c) 485 g to kg

Answer:

1000 g = 1 kg

485 g = (485 ÷ 1000) kg

Final answer: 0.485 kg