Kathy left home at 10.55 a.m. and drove towards the countryside. 3 hours later, her grandfather left their home and drove towards the same countryside at 88 km/h. When the grandfather reached the countryside at 6.55 p.m., Kathy had another 4 km to travel. What was Kathy’s average speed? Express your answer in mixed number.
Time that the Kathy's grandfather started driving = 1.55 p.m.
Duration that Kathy's grandfather drove from 1.55 p.m. to 6.55 p.m. = 5 h

Distance that Kathy's grandfather travelled
= 5 x 88
= 440 km

Distance that Kathy travelled by the time her grandfather reached the city
= 440 - 4
= 436 km

Time that Kathy took to travel 436 km = 8 h

Kathy's average speed
= 436 ÷ 8
= 54¹₂ km/h

Answer(s): 54¹₂ km/h