1. What are units?
Units are standard that are used to measure the size of different properties like length, mass and time etc.
There are different standards of units used around the world but two of the most used are Metric units and Imperial units.
| Common Metric Conversions |
| Length |
1 metre |
1000 millimetres |
| 1 metre |
100 centimetres |
| 1 kilometre |
1000 metres |
| Mass |
1 kg |
1000 grams |
| 1 tonnes |
1000 kgs |
| Volume |
1 litre |
1000 cm³ |
| 1 litre |
1000 ml |
| 1 ml |
1 cm³ |
| Common Imperial Conversions |
| Length |
1 foot |
12 inches |
| 1 yard |
3 feet |
| 1 mile |
1760 yards |
| Mass |
1 stone |
14 pounds (lb) |
| 1 pounds |
16 ounces (oz) |
| Volume |
1 pint |
20 ounces (oz) |
| 1 gallons |
8 pints |
Common Metric-Imperial conversions
1 kg ≈ 2.2 pounds
1 foot ≈ 30 cm
1 gallon ≈ 4.5 litres
1 mile ≈ 1.6 km
“ ≈ ” = approximately equal to
From Exams point of view you only need to remember the Metric unit conversions.
1.1 What is Unit conversion?
The process of converting a measurement from one unit to another is called unit conversion. The conversion is performed using multiplying and dividing the conversion factor.
To solve the questions of unit conversion you only need to keep in mind two things. While converting to a smaller unit you need to multiply and while converting to a larger unit you need to divide.
Example: (Larger unit to smaller unit)
Annie rides her bicycle from her home to her friend Breanne's home which is 1.5 km away. What is the distance between their homes in metres?
Example: (smaller unit to larger unit)
Joanna has a water bottle which has a capacity of 750 ml. What is the capacity of her bottle in litres?
1.2 Unit conversion of Times
The conversion relations among different units of time are as follows:
| 1 minute |
60 seconds |
| 1 hour |
60 minutes |
| 1 day |
24 hours |
| 1 month |
7 days |
| 1 year |
365 days
(366 days in a leap year) |
Example:
How many hours are there in the month of April.
1.3 Unit conversion of Money
Any two currencies are converted into each other using an exchange rate, which is subject to change over time so the question will provide you with the conversion.
Example:
The Exchange rate is : £1 = $1.20
Work out how much is £1000 in American dollars ($).
