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Question

Nina and Jo both ran a 9 km race. Nina took 1 hour 15 minutes to run the whole race. Jo started the race 4 minutes later than Nina but caught up when they had both travelled 6 km. If Nina and Jo both ran at constant speeds, what is Jo's speed to 2 dp?

Answer

The speed of Jo is approximately 7.83 km/h. Step-by-step explanation: 1. To find Nina's time for 6 km, we use the proportion: (time for 6 km)/(6 km) = (time for 9 km)/(9 km). 2. Solving for time for 6 km, we get: time for 6 km = (6 km)/(9 km) × (75 min) = 50 min. 3. Jo's time for the same distance will be 4 minutes less than Nina's time, so Jo's time is 50 -4 = 46 min. 4. To find Jo's speed, we use the formula speed = distance/time, with distance being 6km and time being 46/60 h (converted to hours). 5. Solving for Jo's speed, we get: speed = (6 km)/(46/60 h) = 360/46 h ≈ 7.83 km/h. Additional comment: From the 6 km point, the remaining race is half the distance already run, so it will take half the time already taken. As we know, Nina will finish in 25 more minutes; Jo will finish in 46/2 = 23 more minutes, 2 minutes ahead of Nina.