Fiona left home at 11.15 a.m. and drove towards the campsite. 3 hours later, her younger brother left their home and drove towards the same campsite at 89 km/h. When the younger brother reached the campsite at 7.15 p.m., Fiona had another 5 km to travel. What was Fiona’s average speed? Express your answer in mixed number.
Time that the Fiona's younger brother started driving = 2.15 p.m.
Duration that Fiona's younger brother drove from 2.15 p.m. to 7.15 p.m. = 5 h

Distance that Fiona's younger brother travelled
= 5 x 89
= 445 km

Distance that Fiona travelled by the time her younger brother reached the city
= 445 - 5
= 440 km

Time that Fiona took to travel 440 km = 8 h

Fiona's average speed
= 440 ÷ 8
= 55 km/h

Answer(s): 55 km/h