Arunner wants to be able to run 400m in 50 seconds. what miles per hour speed must have runner attain to accomplish this goal. the runner knows that there are 1609 meters in a mile

Expected speed: 400 m in 50 seconds 
Therefore, speed in m/sec = 8 m/sec 
Given: 1 mile =1609 meters 
1 meter = 1/1609 miles 
 1 hour = 60 sec x 60 sec =3600 seconds 
 1 second = 1/3600 hour 
 To convert meters to miles, we should multiply it by 1/1609
 To convert seconds to hour, we should multiply it by 1/3600 
 Therefore, 8 m/sec = 8 x (1/1609) Ă· (1/3600) 
 = (8 x 3600)/1609
  =17.9 miles / hr