Olivia left home at 11.15 a.m. and drove towards the countryside. 3 hours later, her grandfather left their home and drove towards the same countryside at 97 km/h. When the grandfather reached the countryside at 7.15 p.m., Olivia had another 3 km to travel. What was Olivia’s average speed? Express your answer in mixed number.
Time that the Olivia's grandfather started driving = 2.15 p.m.
Duration that Olivia's grandfather drove from 2.15 p.m. to 7.15 p.m. = 5 h

Distance that Olivia's grandfather travelled
= 5 x 97
= 485 km

Distance that Olivia travelled by the time her grandfather reached the city
= 485 - 3
= 482 km

Time that Olivia took to travel 482 km = 8 h

Olivia's average speed
= 482 ÷ 8
= 60¹₄ km/h

Answer(s): 60¹₄ km/h