Olivia left home at 11.50 a.m. and drove towards the seaside resort. 2 hours later, her grandmother left their home and drove towards the same seaside resort at 98 km/h. When the grandmother reached the seaside resort at 4.50 p.m., Olivia had another 5 km to travel. What was Olivia’s average speed? Express your answer in mixed number.
Time that the Olivia's grandmother started driving = 1.50 p.m.
Duration that Olivia's grandmother drove from 1.50 p.m. to 4.50 p.m. = 3 h

Distance that Olivia's grandmother travelled
= 3 x 98
= 294 km

Distance that Olivia travelled by the time her grandmother reached the city
= 294 - 5
= 289 km

Time that Olivia took to travel 289 km = 5 h

Olivia's average speed
= 289 ÷ 5
= 57⁴₅ km/h

Answer(s): 57⁴₅ km/h