Final answer:
To find Jo's speed, we divide the distance both runners traveled when Jo caught up (9 km) by Jo's running time, which was 59.5 minutes. Jo's speed is therefore calculated to be 9.08 km/h to two decimal places.
Step-by-step explanation:
To calculate Jo's speed, let's consider the information given. Nina took 1 hour and 30 minutes (which is 90 minutes, or 5400 seconds) to complete the 12 km race, meaning that Nina's speed was 12 km divided by 1.5 hours (or 12 km divided by 90 minutes). This can be written as:
Nina's speed = 12 km / 1.5 hours = 8 km/h.
Jo started the race 8 minutes later and caught up with Nina at the 9 km mark. The time Nina took to reach the 9 km mark can be calculated using her speed:
Time Nina took to reach 9 km = Distance / Speed = 9 km / 8 km/h = 1.125 hours (or 67.5 minutes).
Since Jo started 8 minutes after Nina, the time Jo had to cover the same distance was 67.5 minutes - 8 minutes = 59.5 minutes. To find Jo's speed, we divide the distance Jo traveled by the time Jo took:
Jo's speed = Distance / Time = 9 km / (59.5 minutes / 60)
= 9 km / 0.99167 hours,
= 9.084 km/h.
Therefore, Jo's speed to two decimal places is 9.08 km/h.