Winnie left home at 10.20 a.m. and drove towards the seaside resort. 3 hours later, her older sister left their home and drove towards the same seaside resort at 91 km/h. When the older sister reached the seaside resort at 6.20 p.m., Winnie had another 3 km to travel. What was Winnie’s average speed? Express your answer in mixed number.
Time that the Winnie's older sister started driving = 1.20 p.m.
Duration that Winnie's older sister drove from 1.20 p.m. to 6.20 p.m. = 5 h

Distance that Winnie's older sister travelled
= 5 x 91
= 455 km

Distance that Winnie travelled by the time her older sister reached the city
= 455 - 3
= 452 km

Time that Winnie took to travel 452 km = 8 h

Winnie's average speed
= 452 ÷ 8
= 56¹₂ km/h

Answer(s): 56¹₂ km/h