Question

Usain Bolt set the world record for sprinting 100 m in approximately 9 3/5 seconds. Find his average speed in meters per second.

Answer 1

Let's find the seconds as an improper fraction:

`9(3)/(5)=9+(3)/(5)=(9*5)/(5)+(3)/(5)=(48)/(5)=9.6`

He ran 100 meters in 48/5 seconds or 9.6 seconds. To find the speed in meters per second we have to divide the distance (in meters) by the time (in seconds):

`\text{speed}=(100m)/((48)/(5)s)=(5*100m)/(48s)=(125)/(12)\approx10.41\bar{6}`

The average speed is 125/12 m/s (or 10.42 m/s, rounded to the nearest hundredth)

In mixed numbers the speed is 10 5/12 m/s