In some problems, measurements must be converted between metric and Imperial units. The required conversion facts are given and must be used accurately. Careful handling of units is essential to avoid errors.

 

 

Understanding Metric and Imperial Systems

The metric system uses units such as metres, kilometres, grams and litres.

 

The Imperial system uses units such as miles, inches, feet, pounds, ounces, pints and gallons.

 

When converting between systems, you must:
• use the given equivalence
• multiply or divide correctly
• include the correct unit in the final answer

 

 

Metric to Imperial Equivalences

The following equivalences are commonly provided:

• \( 1\ mile \approx 1.6\ km \)
• \( 1\ inch \approx 2.54\ cm \)
• \( 1\ foot \approx 30\ cm \)
• \( 1\ lb \approx 0.45\ kg \)
• \( 1\ ounce \approx 28\ g \)
• \( 1\ pint \approx 0.57\ litres \)
• \( 1\ gallon \approx 4.5\ litres \)

 

These values are used to convert in either direction.

 

 

Converting Kilometres and Miles

To convert kilometres to miles:
• divide by 1.6

 

To convert miles to kilometres:
• multiply by 1.6

 

Example
A distance of 8 km is approximately 5 miles.

 

 

Converting Centimetres and Metres to Inches and Feet

To convert centimetres to inches:
• divide by 2.54

 

To convert inches to centimetres:
• multiply by 2.54

 

To convert metres to feet:
• divide by 0.3

 

To convert feet to metres:
• multiply by 0.3

 

Always check whether the measurement is given in centimetres or metres before converting.

 

 

Converting Kilograms, Pounds, Grams and Ounces

To convert kilograms to pounds:
• divide by 0.45

 

To convert pounds to kilograms:
• multiply by 0.45

 

To convert grams to ounces:
• divide by 28

 

To convert ounces to grams:
• multiply by 28

 

Mass conversions often require rounding to a sensible level of accuracy.

 

 

Converting Litres, Pints and Gallons

To convert litres to pints:
• divide by 0.57

 

To convert pints to litres:
• multiply by 0.57

 

To convert gallons to litres:
• multiply by 4.5

 

To convert litres to gallons:
• divide by 4.5

 

Always state the final unit clearly.

 

 

Choosing the Correct Conversion

Before calculating, always:
• identify which unit you are starting with
• identify which unit you need to convert to
• select the correct equivalence
• decide whether to multiply or divide

 

Using the wrong operation is the most common source of error

 

 

Key Points to Remember

Metric and Imperial units use different measurement systems.
Always use the conversion value given in the question.
Multiply or divide depending on the direction of conversion.
Write units clearly in the final answer.
Check whether the result is sensible for the context.

 

Being confident with metric and Imperial conversions allows measurements to be compared and interpreted accurately in real life and mathematical problems.