1. d = rt You must isolate r, so divide by t and you get r = d/t
2. Average speed is the total distance divided by the total time. 400m/43.83s=9.1m/s (Round to the nearest tenth, says in question)
3. Same thing but with Garcia's measurements. 110m/13s=8.5m/s (Round to the nearest tenth, says in question)
4. Kenteris's Speed = 200m/20.09s=9.9552m/s (Do not round until final answer) Johnson's Speed = 200m/19.32s=10.3520m/s
10.3520m/s - 9.9552m/s = .4 m/s (Round to the nearest tenth, says in question) The difference in speed is found by simply subtracting. Johnson went .4 m/s faster on on average than Kenteris.