Answer:
9.41 km/h
Explanation:
The total distance of the race, d = 8 km
The time Sarah took to run the race, t = 55 mins
The time Jo started the race = 3 mins later than Sara
The point Jo caught up with Sarah = 6 km into the race
The rate at which Jo and Sarah ran = Constant speed
The required information = Jo's speed
From the information given, Sarah's speed, v = 8 km/(55 mins) = (8/55) km/min × 60min/h = 96/11 km/h
The time it would take Sarah to run 6 km = 6 km/(8 km/(55 mins)) = 41.25 mins
Given that Jo started 3 minutes late, and they both arrive at 6 km into the race at the same point in time, the time it took Jo to arrive at 6 km into the race = The time it took Sarah - 3 minutes
∴ The time it took Jo to run the 6 km = 41.25 minutes - 3 minutes = 38.25 minutes
Given that Jo ran at a constant speed, and speed = distance/time, we have;
Jo's speed = 6 km/(38.25 min) = 8/51 km/min × 60 min/h = (160/17) km/h ≈ 9.41 km/h.