Xylia left home at 11.20 a.m. and drove towards the city. 2 hours later, her grandfather left their home and drove towards the same city at 72 km/h. When the grandfather reached the city at 6.20 p.m., Xylia had another 3 km to travel. What was Xylia’s average speed? Express your answer in mixed number.
Time that the Xylia's grandfather started driving = 1.20 p.m.
Duration that Xylia's grandfather drove from 1.20 p.m. to 6.20 p.m. = 5 h

Distance that Xylia's grandfather travelled
= 5 x 72
= 360 km

Distance that Xylia travelled by the time her grandfather reached the city
= 360 - 3
= 357 km

Time that Xylia took to travel 357 km = 7 h

Xylia's average speed
= 357 ÷ 7
= 51 km/h

Answer(s): 51 km/h