Jen left home at 11.15 a.m. and drove towards the seaside resort. 2 hours later, her grandmother left their home and drove towards the same seaside resort at 91 km/h. When the grandmother reached the seaside resort at 4.15 p.m., Jen had another 6 km to travel. What was Jen’s average speed? Express your answer in mixed number.
Time that the Jen's grandmother started driving = 1.15 p.m.
Duration that Jen's grandmother drove from 1.15 p.m. to 4.15 p.m. = 3 h

Distance that Jen's grandmother travelled
= 3 x 91
= 273 km

Distance that Jen travelled by the time her grandmother reached the city
= 273 - 6
= 267 km

Time that Jen took to travel 267 km = 5 h

Jen's average speed
= 267 ÷ 5
= 53²₅ km/h

Answer(s): 53²₅ km/h