Worked example 1 (i) Alex runs a 400 m race in a time of 50 seconds. What is his average speed?
(ii) Claire took part in a cross-country race and completed the course in 1 hour and 12 minutes. Her average speed for the race was 17·5 km per hour. What was the distance that she ran?
(iii) Jane runs at an average speed of 4 metres per second. How long will it take her to run a 3 000-metre race at this pace?
Solution (i) (ii)
Worked example 2
Use the ratio method to calculate the speed of a journey of 45 km if it takes one and a half hours to complete.
Solution
We can also use the ratio method to fi nd the time or distance.
Worked example 3 Find the time taken to complete a journey of 200 m at a speed of 40 m/s.