Year 10 Interactive Maths - Second Edition

Rates

For example, the speed of a train is described as the distance travelled (km) per hour.

We usually write a rate using per or / to indicate that a quantity changes for each unit of time.
For example, the speed of a train is 60 km per hour or 60 km/h.

Some common rates are:

• water rate per quarter
• council rate per quarter
• currency exchange rate
• telephone rental rate
• telephone charge per call

Abbreviations used to describe common rates include:

• L/km means litres per kilometre
• cm/s means centimetres per second
• m/min means metres per minute
• L/min means litres per minute
• ¢/min means cents per minute
• ¢/L means cents per litre

Example 5

Find the speed of a walker if he walks 24 kilometres in 3 hours.

Solution:

So, the speed of the walker is 8 km/h.

Example 6

Find the telephone call charge rate if a telecommunications company charges $1.80 for 12 calls.

Solution:

So, the rate is 15¢/call.

Example 7

Find the rate of reading if a student read 432 pages of a book in 16 days.

Solution:

So, the rate of reading is 27 pages/day.

Example 8

Solution:

Key Terms

rate, speed