Rates

A rate is a ratio that involves two different units. A rate is usually expressed as an amount per unit, such as ‘price per ticket’ or ‘kilometres per hours’.

Example 1: Cameron’s car uses 9 litres of petrol to travel 100 km. a) calculate the km/L b) calculate the L/km

Example 1: Cameron’s car uses 9 litres of petrol to travel 100 km. a) calculate the km/L

Example 1: Cameron’s car uses 9 litres of petrol to travel 100 km. b) calculate the L/km

Example 2: A baby requires 150 mL of fluid per kg of weight every 24 hours. When Tim was 12 weeks old he weighed 4.8kg. a) How many mL of fluid did he require per 24 hours? b) At this age his mother gave him four bottles of fluid each day. How many mL were in each bottle?

Example 2: A baby requires 150 mL of fluid per kg of weight every 24 hours. When Tim was 12 weeks old he weighed 4.8kg. a) How many mL of fluid did he require per 24 hours? mL of fluid required = 150 mL x kg of weight - = 150 mL x 4.8kg = 720 mL

Example 2: A baby requires 150 mL of fluid per kg of weight every 24 hours. When Tim was 12 weeks old he weighed 4.8kg. b) At this age his mother gave him four bottles of fluid each day. How many mL were in each bottle? 4 bottles = 720 mL 1 bottle = 720 ÷ 4 = 180 mL

Example 3: Usain Bolt can run 100 metres in approx 9.6 seconds. Angus can run the same distance in 12 seconds. a) How far apart would Usain and Angus be (in km) after one hour (presuming they can maintain the same speed)? b) What is Usain Bolt’s speed in km/hour?