Winnie left home at 11.50 a.m. and drove towards the province. 3 hours later, her grandmother left their home and drove towards the same province at 87 km/h. When the grandmother reached the province at 7.50 p.m., Winnie had another 5 km to travel. What was Winnie’s average speed? Express your answer in mixed number.
Time that the Winnie's grandmother started driving = 2.50 p.m.
Duration that Winnie's grandmother drove from 2.50 p.m. to 7.50 p.m. = 5 h

Distance that Winnie's grandmother travelled
= 5 x 87
= 435 km

Distance that Winnie travelled by the time her grandmother reached the city
= 435 - 5
= 430 km

Time that Winnie took to travel 430 km = 8 h

Winnie's average speed
= 430 ÷ 8
= 53³₄ km/h

Answer(s): 53³₄ km/h