Yen left home at 10.50 a.m. and drove towards the province. 3 hours later, her grandfather left their home and drove towards the same province at 84 km/h. When the grandfather reached the province at 6.50 p.m., Yen had another 2 km to travel. What was Yen’s average speed? Express your answer in mixed number.
Time that the Yen's grandfather started driving = 1.50 p.m.
Duration that Yen's grandfather drove from 1.50 p.m. to 6.50 p.m. = 5 h

Distance that Yen's grandfather travelled
= 5 x 84
= 420 km

Distance that Yen travelled by the time her grandfather reached the city
= 420 - 2
= 418 km

Time that Yen took to travel 418 km = 8 h

Yen's average speed
= 418 ÷ 8
= 52¹₄ km/h

Answer(s): 52¹₄ km/h