Fanny left home at 11.15 a.m. and drove towards the suburb. 2 hours later, her grandmother left their home and drove towards the same suburb at 91 km/h. When the grandmother reached the suburb at 5.15 p.m., Fanny had another 4 km to travel. What was Fanny’s average speed? Express your answer in mixed number.
Time that the Fanny's grandmother started driving = 1.15 p.m.
Duration that Fanny's grandmother drove from 1.15 p.m. to 5.15 p.m. = 4 h

Distance that Fanny's grandmother travelled
= 4 x 91
= 364 km

Distance that Fanny travelled by the time her grandmother reached the city
= 364 - 4
= 360 km

Time that Fanny took to travel 360 km = 6 h

Fanny's average speed
= 360 ÷ 6
= 60 km/h

Answer(s): 60 km/h