Cathy left home at 11.20 a.m. and drove towards the province. 3 hours later, her older sister left their home and drove towards the same province at 86 km/h. When the older sister reached the province at 7.20 p.m., Cathy had another 2 km to travel. What was Cathy’s average speed? Express your answer in mixed number.
Time that the Cathy's older sister started driving = 2.20 p.m.
Duration that Cathy's older sister drove from 2.20 p.m. to 7.20 p.m. = 5 h

Distance that Cathy's older sister travelled
= 5 x 86
= 430 km

Distance that Cathy travelled by the time her older sister reached the city
= 430 - 2
= 428 km

Time that Cathy took to travel 428 km = 8 h

Cathy's average speed
= 428 ÷ 8
= 53¹₂ km/h

Answer(s): 53¹₂ km/h