Marion left home at 11.45 a.m. and drove towards the town. 2 hours later, her cousin left their home and drove towards the same town at 84 km/h. When the cousin reached the town at 5.45 p.m., Marion had another 6 km to travel. What was Marion’s average speed? Express your answer in mixed number.
Time that the Marion's cousin started driving = 1.45 p.m.
Duration that Marion's cousin drove from 1.45 p.m. to 5.45 p.m. = 4 h

Distance that Marion's cousin travelled
= 4 x 84
= 336 km

Distance that Marion travelled by the time her cousin reached the city
= 336 - 6
= 330 km

Time that Marion took to travel 330 km = 6 h

Marion's average speed
= 330 ÷ 6
= 55 km/h

Answer(s): 55 km/h