Barbara left home at 10.55 a.m. and drove towards the town. 3 hours later, her mother left their home and drove towards the same town at 86 km/h. When the mother reached the town at 6.55 p.m., Barbara had another 6 km to travel. What was Barbara’s average speed? Express your answer in mixed number.
Time that the Barbara's mother started driving = 1.55 p.m.
Duration that Barbara's mother drove from 1.55 p.m. to 6.55 p.m. = 5 h

Distance that Barbara's mother travelled
= 5 x 86
= 430 km

Distance that Barbara travelled by the time her mother reached the city
= 430 - 6
= 424 km

Time that Barbara took to travel 424 km = 8 h

Barbara's average speed
= 424 ÷ 8
= 53 km/h

Answer(s): 53 km/h