Shiyun left home at 11.20 a.m. and drove towards the province. 3 hours later, her cousin left their home and drove towards the same province at 88 km/h. When the cousin reached the province at 7.20 p.m., Shiyun had another 4 km to travel. What was Shiyun’s average speed? Express your answer in mixed number.
Time that the Shiyun's cousin started driving = 2.20 p.m.
Duration that Shiyun's cousin drove from 2.20 p.m. to 7.20 p.m. = 5 h

Distance that Shiyun's cousin travelled
= 5 x 88
= 440 km

Distance that Shiyun travelled by the time her cousin reached the city
= 440 - 4
= 436 km

Time that Shiyun took to travel 436 km = 8 h

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

Answer(s): 54¹₂ km/h