Xuan left home at 11.25 a.m. and drove towards the seaside resort. 2 hours later, her grandmother left their home and drove towards the same seaside resort at 92 km/h. When the grandmother reached the seaside resort at 4.25 p.m., Xuan had another 3 km to travel. What was Xuan’s average speed? Express your answer in mixed number.
Time that the Xuan's grandmother started driving = 1.25 p.m.
Duration that Xuan's grandmother drove from 1.25 p.m. to 4.25 p.m. = 3 h

Distance that Xuan's grandmother travelled
= 3 x 92
= 276 km

Distance that Xuan travelled by the time her grandmother reached the city
= 276 - 3
= 273 km

Time that Xuan took to travel 273 km = 5 h

Xuan's average speed
= 273 ÷ 5
= 54³₅ km/h

Answer(s): 54³₅ km/h