Olivia left home at 11.50 a.m. and drove towards the suburb. 2 hours later, her mother left their home and drove towards the same suburb at 97 km/h. When the mother reached the suburb at 4.50 p.m., Olivia had another 4 km to travel. What was Olivia’s average speed? Express your answer in mixed number.
Time that the Olivia's mother started driving = 1.50 p.m.
Duration that Olivia's mother drove from 1.50 p.m. to 4.50 p.m. = 3 h

Distance that Olivia's mother travelled
= 3 x 97
= 291 km

Distance that Olivia travelled by the time her mother reached the city
= 291 - 4
= 287 km

Time that Olivia took to travel 287 km = 5 h

Olivia's average speed
= 287 ÷ 5
= 57²₅ km/h

Answer(s): 57²₅ km/h